MSX2 TECHNICAL HANDBOOK ----------------------- Edited by: ASCII Systems Division Published by: ASCII Coprporation - JAPAN First edition: March 1987 Text file typed by: Nestor Soriano (Konami Man) - SPAIN October 1997 Changes from the original: - In Figure 5.2, unused bits are marked as "x", and inverted signals are marked with "*", for easiest readability. - Figure 5.17B was added. - In List 5.4, the last line before the work area, "JR START", has been corrected to "JR SCAN". - In Figure 5.18, the addresses for GETPNT y PUTPNT were swapped. They have been corrected. - In description of BIOS routines PINLIN and INLIN, "BUF" address has been corrected from F55DH to F55EH. - In Figure 5.22 (B), "Arabaic mode display" has been changed to "Arabic or kana mode display". - In description of BIOS routine GTTRIG, the input needed for reading B buttons has been added in the "Input" field. - In Table 5.5, in the Note 4, "the trigger button of the mouse or the trigger button" has been changed to "the trigger button of the mouse or the trigger button of the track ball". - In Figure 5.29, "1200 or 2400 hours" indication has been corrected to "12 or 24 hours". - In Figure 5.32, "Register 3 #11" indication has been corrected to "Register #11". - In Figure 5.33, "Adjust Y (8 to +7)" has been corrected to "Adjust Y (-8 to +7)". - In description of BIOS routine WRTCLK, the input needed in the A register has been added in the "Input" field. -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- CHAPTER 5 - ACCESS TO PERIPHERALS THROUGH BIOS (Parts 1 to 6) The basic philosophy of MSX is to have a standard interface, independent of machines or versions, to access peripherals through BIOS. Thus, the user should get to know about using BIOS first. In chapter 5, accessing peripherals using BIOS and the structure used for each peripheral are described. 1. PSG AND SOUND OUTPUT MSX has the following three kinds of sound output functions, but function (3) is not installed in the standard MSX, so it is not described in this manual. This section describes functions (1) and (2). (1) PSG sound output (3 channels, 8 octaves) (2) Sound output by 1 bit I/O port (3) Sound output by MSX-AUDIO (FM sound generator) ........ not described in this manual 1.1. PSG functions An AY-3-8910 compatible LSI is used for the MSX music play function and for BEEP tone generation. This LSI is referred to as the PSG (Programmable Sound Generator), and can generate complex music and varios tones. It has the following features: * There are three tone generators, each of which can independently specify 4096 scales (equivalent to 8 octaves) and 16 volume levels. * It can generate piano and organ tones by using envelope patterns. Note that, since there is only one envelope generator, the tone of only one channel can be modified fundamentally. * With the noise generator inside, tones such as the wind or waves can easily be generated. Note that since there is only one noise generator, only one channel can generate the noise. * Any necessary frequency, such as the tone or the envelope, is obtained by dividing the input clock (in MSX, it is defined that fc = 1.7897725 MHz). So there is no unsteady pitch or rythm. Figure 5.1 PSG block diagram R0, R1 R7 R8 -------------------- ------------- ------------------------------ | Tone generator A | --> | | ------> | Volume control amplifier A | -------------------- | | +--> ---------------------------+-- | | | Channel A output <--+ R2, R3 | Three | | R9 -------------------- | | | ------------------------------ | Tone generator B | --> | Channel | ---:--> | Volume control amplifier B | -------------------- | | +--> ---------------------------+-- | Mixer | | Channel B output <--+ R4, R5 | | | R9 -------------------- | | | ------------------------------ | Tone generator C | --> | | ---:--> | Volume control amplifier C | -------------------- ------------- +--> ---------------------------+-- ^ | Channel C output <--+ | | R6 | | R11, R12, R13 --------------------- ------------------------ | Noise generator | | Envelope generator | --------------------- ------------------------ The PSG has two additional I/O (input/output) ports used for other than tone generating functions, which are omitted in the block diagram above. MSX uses them as general-purpose I/O ports to connect to I/O devices such as joystick, a touch pad, a paddle, or a mouse. These general-purpose I/O ports are described in section 5. * PSG registers Since the PSG generates tones, the CPU simply notifies PSG when the tone is to be changed. This is done by writing values in 16 8-bit registers inside the PSG as shown in Figure 5.2. Roles and uses of these registers are described below. * Setting the tone frequency (R0 to R5) Each tone frequency of channel A, B, and C is set by R0 to R5. The input clock frequency (fc = 1.7897725 MHz) is divided by 16 and the result is the standard frequency. Each channel divides the standard frequency by the 12-bit data assigned for each, and the objective pitch is obtained. The following relation exists between 12-bit data (TP) and the tone frequency to be generated (ft). ft = fc/(16 * TP) = 0.11186078125/TP [MHz] = 111860.78125/TP [Hz] A 12-bit data TP is specified for each channel by 4 high order bit coarse tune CT and 8 low order bit fine tune value FT, as shown in Figure 5.3. Table 5.1 shows the register settings to make the scales. Figure 5.2 PSG register structure ----------------------------------------------------------------------------- | Bit | | | | | | | | | | | B7 | B6 | B5 | B4 | B3 | B2 | B1 | B0 | | Register | | | | | | | | | |---------------------------+-----------------------------------------------| | R0 | Channel A note | 8 low order bits | |----------| |-----------------------------------------------| | R1 | Dividing rate | x x x x | 4 high order bits | |----------+----------------+-----------------------------------------------| | R2 | Channel B note | 8 low order bits | |----------| |-----------------------------------------------| | R3 | Dividing rate | x x x x | 4 high order bits | |----------+----------------+-----------------------------------------------| | R4 | Channel C note | 8 low order bits | |----------| |-----------------------------------------------| | R5 | Dividing rate | x x x x | 4 high order bits | |----------+----------------+-----------------------------------------------| | R6 | Noise div. rate| x x x | | |----------+----------------+-----------------------------------------------| | | | IN*/OUT | NOISE* | TONE* | | R7 | Enable* |-----------+-----------------+-----------------| | | | IOB | IOA | C | B | A | C | B | A | |----------+----------------+-----------------+-----+-----------------------| | R8 | Chan. A volume | x x x | M | | |----------+----------------+-----------------+-----+-----------------------| | R9 | Chan. B volume | x x x | M | | |----------+----------------+-----------------+-----+-----------------------| | R10 | Chan. C volume | x x x | M | | |----------+----------------+-----------------------------------------------| | R11 | | 8 low order bits | |----------| Envelope Cycle |-----------------------------------------------| | R12 | | 8 high order bits | |----------+----------------+-----------------------------------------------| | R13 | Env. wave shape| x x x x | | |----------+----------------+-----------------------------------------------| | R14 | I/O port A | | |----------+----------------+-----------------------------------------------| | R15 | I/O port B | | ----------------------------------------------------------------------------- NOTE: x = unused bit * = inverted signal Figure 5.3 Setting the pitch ------------------------------------------------- R0, R2, R4 | 8 bits | --+ ------------------------------------------------- | ------------------------------------------------- | R0, R2, R4 | x x x x | 4 bits | | ------------------------------------------------- | | | ----------------------------------------+ | | | V V ----------------------------------------------------------------------- | Coarse Tune (CT) | Fine Tune (FT) | ----------------------------------------------------------------------- | | +-------------------------------- TP ---------------------------------+ [ Channel A - R0, R1 ] [ Channel B - R2, R3 ] [ Channel C - R4, R5 ] Table 5.1 Setting the tone frequency (scale data) ---------------------------------------------------------------- | Octave | | | | | | | | | | | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | | Note | | | | | | | | | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | C | D5D | 6AF | 357 | 1AC | D6 | 6B | 35 | 1B | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | C# | C9C | 64E | 327 | 194 | CA | 65 | 32 | 19 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | D | BE7 | 5F4 | 2FA | 17D | BE | 5F | 30 | 18 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | D# | B3C | 59E | 2CF | 168 | 84 | 5A | 2D | 16 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | E | A9B | 54E | 2A7 | 153 | AA | 55 | 2A | 15 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | F | A02 | 501 | 281 | 140 | A0 | 50 | 28 | 14 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | F# | 973 | 4BA | 25D | 12E | 97 | 4C | 26 | 13 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | G | 8EB | 476 | 23B | 11D | 8F | 47 | 24 | 12 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | G# | 88B | 436 | 21B | 10D | 87 | 43 | 22 | 11 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | A | 7F2 | 3F9 | 1FD | FE | 7F | 40 | 20 | 10 | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | A# | 780 | 3C0 | 1E0 | F0 | 78 | 3C | 1E | F | |--------------+-----+-----+-----+-----+-----+-----+-----+-----| | B | 714 | 38A | 1C5 | E3 | 71 | 39 | 1C | E | ---------------------------------------------------------------- * Setting the noise frequency (R6) The noise generator is used for synthesizing explosion sounds or wave sounds. The PSG can send the noise output by the noise generator to channels A to C. Since there is only one noise generator, the same noise is sent to all channels. By changing the average frequency, various noise effects can be obtained and this is done by R6 register settings. The 5 low order bit data (NP) of this register is divides into the standard frequency (fc/16) and this determines the average frequency of the noise (fn). Figure 5.4 Setting the noise frequency ------------------------------------------------- R6 | x x x | | ------------------------------------------------- | | +------------- NP ------------+ The following relation exists between NP and fn. fn = fc/(16 * NP) = 0.11186078125/NP [MHz] = 111860.78125/NP [Hz] Since the value of NP is from 1 to 31, the average frequency of the noise can be set from 3.6kHz to 111.9kHz. * Mixing the sound (R7) R7 is used to select the output of the tone and noise generator, or a mixture of both. As shown in Figure 5.5, the 3 low order bits (B0 to B2) of R7 control the tone output and the next 3 bits (B3 to B5) control the noise output. In both cases, when the corresponding bit is 0, the output is ON and, when 1, it is OFF. Figure 5.5 Output selection for each channel ------------------------------------------------- R7 | B7 | B6 | B5 | B4 | B3 | B2 | B1 | B0 | ------------------------------------------------- | | V B7 B6 B5 B4 B3 B2 B1 B0 ----------------- ------------------------- ------------------------- | Input enable* | | Noise enable* | | Tone enable* | |---------------| |-----------------------| |-----------------------| | B | A | | C | B | A | | C | B | A | ----------------- ------------------------- ------------------------- I/O port Noise output Tone output Input - 0 ON - 0 ON - 0 Output - 1 OFF - 1 OFF - 1 The 2 high order bits of R7 do not affect sound output. These are used to determine the direction of the data of two I/O ports which PSG has. When the corresponding bit is 0, the input mode is selected and, when 0, the output mode is selected. In MSX, port A is used for the input and port B for the output, so it should always be set so that bit 6 = "0" and bit 7 = "1". * Setting the volume (R8 to R10) R8 to R10 are used to specify the volume of each channel. Two ways can be selected by these registers: specifying the fixed volume by 4-bit data (0 to 15) and generating sound effects such as vibrato or fade-out by using the envelope. Figure 5.6 Setting the volume ------------------------------------------------- R8, R9, R10 | x x x | B4 | B3 | B2 | B1 | B0 | ------------------------------------------------- | | | | +---------- L ----------+ | V Use envelope: No - 0 (set volume by the value of L) Yes - 1 (ignore the value of L) When bit 4 of these registers is "0", the envelope is not used and the 4 low order bit value L (0 to 15) of the registers specify the volume. When bit 4 is "1", the volume depends on the envelope signals and the value L is ignored. * Setting the envelope cycle (R11, R12) R11 and R12 specify the envelope cycle in 16-bit data. The 8 high order bits are set in R12 and the 8 low order bits are set in R11. Figure 5.7 Setting the envelope cycle ------------------------------------------------- R11 | | --+ ------------------------------------------------- | ------------------------------------------------- | R12 | | | ------------------------------------------------- | | | ---------------------------------+ | | | V V ----------------------------------------------------------------------------- | Coarse Tune (CT) | Fine Tune (FT) | ----------------------------------------------------------------------------- | | +----------------------------------- EP ------------------------------------+ The following relation exists between the envelope cycle T and 16-bit data EP. T = (256 * EP) / fc = (256 * EP) / 1.787725 [MHz] = 143.03493 * EP [micro second] * Setting the envelope pattern (R13) R13 sets the envelope pattern by the 4 low order bit data as shown in Figure 5.8. The intervals of T specified in the figure correspond to the envelope cycle specified by R11 and R12. Figure 5.8 Setting the wave forms of the envelopes ------------------------------------------------- R13 | x x x x | B3 | B2 | B1 | B0 | ------------------------------------------------- | ------------------------------------+ | V --------------------------------------------------------- | | :\ | | 0 0 x x | __: \______________________ | | | | | | /: | | 0 1 x x | __/ :______________________ | | | | | | :\ :\ :\ :\ :\ :\ :\ | | 1 0 0 0 | __: \: \: \: \: \: \:_ | | | | | | :\ | | 1 0 0 1 | __: \______________________ | | | | | | :\ / \ / \ / \ | | 1 0 1 0 | __: \ / \ / \ / | | | _____________________ | | | :\ : | | 1 0 1 1 | __: \: | | | | | | /: /: /: /: /: /: | | 1 1 0 0 | __/ :/ :/ :/ :/ :/ :/ | | | ______________________ | | | / | | 1 1 0 1 | __/ | | | | | | / \ / \ / \ | | 1 1 1 0 | __/ \ / \ / \ / | | | | | | /: | | 1 1 1 1 | __/ :______________________ | | | | --------------------------------------------------------- | | +---+ T * I/O port (R14, R15) R14 and R15 are the ports to send and receive 8-bit data in parallel. MSX uses these as the general-purpose I/O interface. For more information, see section 5. 1.2 Access to the PSG For access the PSG from assembly language programs, several BIOS routines described below are available. * GICINI (0090H/MAIN) .................. PSG initialization Input: --- Output: --- Function: initializes PSG registers and does the initial settings of the work area in which PLAY statement of BASIC is executed. Each register of PSG is set to the value as shown in Figure 5.9. Figure 5.9 Initial values of PSG registers ----------------------------------------------------------------------------- | Bit | | | | | | | | | | | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | | Register | | | | | | | | | |---------------------------+-----------------------------------------------| | R0 | Channel A | 0 1 0 1 0 1 0 1 | |----------| |-----------------------------------------------| | R1 | frequency | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R2 | Channel B | 0 0 0 0 0 0 0 0 | |----------| |-----------------------------------------------| | R3 | frequency | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R4 | Channel C | 0 0 0 0 0 0 0 0 | |----------| |-----------------------------------------------| | R5 | frequency | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R6 | Noise frequency| 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R7 | Channel setting| 1 0 1 1 1 0 0 0 | |----------+----------------+-----------------------------------------------| | R8 | Chan. A volume | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R9 | Chan. B volume | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R10 | Chan. C volume | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R11 | | 0 0 0 0 1 0 1 1 | |----------| Envelope Cycle |-----------------------------------------------| | R12 | | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R13 | Env. pattern | 0 0 0 0 0 0 0 0 | |----------+----------------+-----------------------------------------------| | R14 | I/O port A | | |----------+----------------+-----------------------------------------------| | R15 | I/O port B | | ----------------------------------------------------------------------------- * WRTPSG (0093H/MAIN) ................. writing data in PSG registers Input: A <-- PSG register number E <-- data to be written Output: --- Function: writes the contents of the E register in the PSG register whose number is specified by the A register. * RDPSG (0096H/MAIN) .................. reading PSG register data Input: A <-- PSG register number Output: A <-- contents of the specified register Function: reads the contents of PSG register whose number is specified by the A register and stores the value in the A register. * STRTMS (0099H/MAIN) ................. starting the music Input: (QUEUE) <-- MML which is translated into the intermediate language Output: --- Function: examines whether the music is played as the background task, and plays the music which is set in the queue, if the music has not yet been played. List 5.1 Single tone generation ================================================================= ;************************************************ ; ; List 5.1 440 Hz tone ; ;************************************************ ; WRTPSG EQU 0093H ORG 0B000H ;----- program start ----- LD A,7 ;Select Channel LD E,00111110B ;Channel A Tone := On CALL WRTPSG LD A,8 ;Set Volume LD E,10 CALL WRTPSG LD A,0 ;Set Fine Tune Channel A LD E,0FEH ;Data 0FEH CALL WRTPSG LD A,1 ;Set Coarse Tune Channel A LD E,0 ;Data 0H CALL WRTPSG RET END ================================================================= 1.3 Tone Generation by 1-bit Sound Port MSX has another sound generator in addition to the PSG. This is a simple one that generates sound by turning ON/OFF the 1-bit I/O port output repeatedly using software. Figure 5.10 1-bit sound port bit 7 6 5 4 3 2 1 0 ----------------------------------------- | . | | | | | | | | --+-------------------------------------- | PPI port C (I/O address 0AAH) | | :::::::::::: V : PSG : --------- : output :::::::>| MIX | :::::::::::: --------- | V ----- / \ Speaker --------- / : \ 1.4 Access to 1-bit Sound Port To access to the 1-bit sound port, the following BIOS routine is offered. * CHGSND (0135H/MAIN) Input: A <-- specification of ON/OFF (0 = OFF, others = ON) Output: Function: calling this routine with setting 0 in the A register turns the bit of the sound port OFF; calling it with another value turns it ON. List 5.2 Reading from cassette tape ================================================================= ;******************************************************** ; ; List 5.2 Read from cassette tape ; ; Set music tape into tape-recorder ; and run this program. ; Then your MSX will replay it. ; ;******************************************************** ; CHGSNG EQU 0135H STMOTR EQU 00F3H RDPSG EQU 0096H BREAKX EQU 00B7H ORG 0B000H ;----- program start ----- Note: Play tape using 1-bit sound port. START: LD A,1 ;motor on CALL STMOTR LBL01: LD A,14 ;register 14 CALL RDPSG ;read PSG AND 80H ;check CSAR CALL CHGSNG ;change SOUND PORT CALL BREAKX ;check Ctrl-STOP JR NC,LBL01 XOR A ;stop cassette motor CALL STMOTR RET END ================================================================= 2. CASSETTE INTERFACE Cassette tape recorders are the least expensive external storage devices available for the MSX. Knowledge of the cassette interface is required to treat information in cassette tapes within assembly language programs. This section offers the necessary information. 2.1 Baud Rate The following two baud rates can be used by the MSX cassette interface (see Table 5.2). When BASIC is invoked, 1200bps is set by default. Table 5.2 MSX baud rate ------------------------------------------------ | Baud rate | Characteristics | |-------------+--------------------------------| | 1200 bps | Low speed / high reliability | |-------------+--------------------------------| | 2400 bps | High speed / low reliability | ------------------------------------------------ The baud rate is specified by the fourth parameter of the SCREEN instruction or the second parameter of the CSAVE instruction. Once the baud rate is set, it stays at that value. SCREEN ,,, CSAVE "filename", ( is 1 for 1200bps, 2 for 2400 bps) 2.2 One bit composition One bit data, the basis of I/O, is recorded as shown in Figure 5.11. The pulse width is determined by counting the T-STATE of the CPU, so, while the cassette interface is active, any interrupt is inhibited. The bit data from the cassette can be read through the seventh bit of port B of the general-purpose I/O interface (register 15 of the PSG). This function was used in the program example of List 5.3, section 1 of chapter 5. Figure 5.11 One bit composition -------------------------------------------------------------- | Baud rate | Bit | Wave form | |-----------+-------+----------------------------------------| | | | : ----------- | | | 0 | : | | (1200Hz x 1) | | 1200 | | :_________| | | | |-------+--:-------------------------------------| | baud | | : ------ ------ | | | 1 | : | | | | (2400Hz x 2) | | | | :____| |____| | | |-----------+-------+--:-------------------------------------| | | | : ------ : | | | 0 | : | | : (2400Hz x 1) | | 2400 | | :____| | : | | |-------+--:-------------------:-----------------| | baud | | : --- --- : | | | 1 | : | | | | : (4800Hz x 2) | | | | :__| |__| | : | -----------------------:--:-:----:---------:------------------ | : : : | 2963 T-states (833 micro-sec) +--:-:----:---------+ | : : | 1491 T-states (417 micro-sec) +--:-:----+ | : | 746 T-states (208 micro-sec) +--:-+ | | 373 T-states (104 micro-sec) +--+ 2.3 One byte composition One byte data is recorded in the array of bits as shown in Figure 5.12. There is one "0" bit as the start bit, followed by the 8-bit data body from LSB to MSX and by two "1" bit as the stop bits, so 11 bits are used. Figure 5.12 One byte composition LSB MSB ------------------------------------------------------------------------- | 0 | X | X | X | X | X | X | X | X | 1 : 1 | ------------------------------------------------------------------------- | | | | +-----+-----------------------------------------------+-----------+ Start bit Data Stop bit 2.4 Header Composition The header is the portion where the signal of the specific frequency is recorded on the tape for a certain period. This allows the cassette tape speed to stabilize after it is started, or divides two files. There is a long header and a short header. The long header is used to wait until the motor is stabilized. The baud rate at reading the tape is determined by reading the long header. The short header is used to divide file bodies. Table 5.3 shows the compositions of both. Table 5.3 Header composition ------------------------------------------------------------------ | Baud rate | Header | Header composition | |-------------+--------------+-----------------------------------| | | Long header | 2400 Hz x 16000 (about 6.7 sec) | | 1200 baud |--------------+-----------------------------------| | | Short header | 2400 Hz x 4000 (about 1.7 sec) | |-------------+--------------+-----------------------------------| | | Long header | 4800 Hz x 32000 (about 6.7 sec) | | 2400 baud |--------------+-----------------------------------| | | Short header | 4800 Hz x 8000 (about 1.7 sec) | ------------------------------------------------------------------ 2.5 File Formats MSX BASIC supports the following three kinds of cassette format files. (1) BASIC text file BASIC programs saved with the CSAVE command are recorded in this format. The file is divided into the preceding file header and the succeeding the body. Figure 5.13 Binary file format 6.7 sec 10 bytes 6 bytes ------------------------------------------------------------------------- | | | | | Long header | 0D3H x 10 | File name | | | | | ------------------------------------------------------------------------- | | +----------+ +------------------------------------+ | | ----------------------------------------------------------------------------- | | File header | | File body | | ----------------------------------------------------------------------------- | | +-------------------------------+ +------+ | | -------------------------------------\ \-------------------------------- | Short | / / | | | header | BASIC program \ \ | 00H x 7 | | | / / | | -------------------------------------\ \-------------------------------- 1.7 sec Any length 7 bytes In the file header, ten bytes each of the value 0D3H follow after the long header and six bytes containing the file name are placed after them. In the file body, program body follows the short header and the end of the file is indicated by seven bytes of 00H. (2) ASCII text file BASIC programs saved in ASCII format by the SAVE command and data files created by the OPEN command are recorded in this format. Figure 5.14 ASCII file format 6.7 sec 10 bytes 6 bytes ------------------------------------------------------------------------- | | | | | Long header | 0EAH x 10 | File name | | | | | ------------------------------------------------------------------------- | | +----------+ +------------------------------------+ | | ----------------------------------------------------------------------------- | | File header | | File body | | ----------------------------------------------------------------------------- | | +-------------------------------+ +------+ | | -----------------------------------------------\ \---------------------- | | | | / / | Last | | Block 1 | Block 2 | Block 3 | ..... \ \ .... | block | | | | | / / | . | -----------------------------------------------\ \------------+--------- | | | +-----------+ +-----------+ CTRL+Z (EOF) | | is included in data ------------------------------------------------ | Short | | | header | Data | ..... | | | ------------------------------------------------ 1.7 sec 256 bytes (3) Machine code file Machine code files saved by the BSAVE command are recorded in the following format. In the file header, 10 bytes each of the value 0D0H follow after the long header and 6 bytes containing the file name are placed after them. In the file body, the starting address, the end address, and the entry address are recorded in order after the short header, and the machine codes follow after them. Since the amount of data can be calculated from the starting and ending addresses, there is no special mark for the end of the file. The entry address is the address where the program is executed when the R option of the BLOAD command is used. Figure 5.15 Machine code file format 6.7 sec 10 bytes 6 bytes ------------------------------------------------------------------------- | | | | | Long header | 0D0H x 10 | File name | | | | | ------------------------------------------------------------------------- | | +----------+ +------------------------------------+ | | ----------------------------------------------------------------------------- | | File header | | File body | | ----------------------------------------------------------------------------- | | +-------------------------------+ +------+ | | ------------------------------------------------------------------------- | Short | Top | End | Starting | | | header | address | address | address | Program body | | | | | | | ------------------------------------------------------------------------- 1.7 sec 2 bytes 2 bytes 2 bytes 2.6 Access to cassette files The following BIOS routines are offered to access cassette files. * TAPION (00E1H/MAIN) ................. OPEN for read Input: --- Output: CY flag = ON at abnormal terminations Function: starts the motor of the tape recorder and reads the long header or the short headet. At the same time, the baud rate in which the file is recorded is detected and the work area is set according to it. Interrupts are inhibited. * TAPIN (00E4H/MAIN) .................. read one byte Input: --- Output: A <-- data which has been read CY flag = ON at abnormal terminations Function: reads one byte of data from the tape and stores it in the A register. * TAPIOF (00E7H/MAIN) ................. CLOSE for read Input: --- Output: --- Function: ends reading from the tape. At this point, interrupts are allowed. * TAPOON (00EAH/MAIN) ................. OPEN for write Input: A <-- type of header (0 = short header, others = long header) Output: CY flag = ON at abnormal terminations Function: starts the motor of the tape recorder and writes the header of the type specified in the A register to the tape. Interrupts are inhibited. * TAPOUT (00EDH/MAIN) ................. write one byte Input: A <-- data to be written Output: CY flag = ON at abnormal terminations Function: writes the contents of the A register to the tape. * TAPOOF (00F0H/MAIN) ................. CLOSE writing Input: --- Output: --- Function: ends writing the tape. At this point, interrupts are allowed. * STMOTR (00F3/MAIN) .................. specify the actions of the motor Input: A <-- action (0 = stop, 1 = start, 255 = reverse the current status) Output: --- Function: sets the status of the motor according to the value specified in the A register. When READ/WRITE routines for the cassette files are created using these BIOS calls, only READ or WRITE, without any other action, should be done. For example, reading data from the tape and displaying it on the CRT might cause a READ error. List 5.3 is a sample program which uses BIOS routines. List 5.3 Listing names of files saved in the cassette ========================================================================= ;************************************************************ ; ; List 5.3 Cassette files ; ; Set cassette tape into recorder and run this program. ; Then all the names and attributes of the programs ; in that tape will be listed. ; ;************************************************************ ; CHPUT EQU 00A2H TAPION EQU 00E1H TAPIN EQU 00E4H TAPIOF EQU 00E7H ORG 0C000H ;----- program start ----- Note: View program names on cassette tape. START: CALL TAPION ;motor on and read header LD B,16 LD HL,WORK ;work area address LBL01: PUSH HL PUSH BC CALL TAPIN ;read a byte of data from tape POP BC POP HL JR C,ERROR ;set carry flag if read error LD (HL),A INC HL DJNZ LBL01 LD HL,FILNAM ;write file name CALL PUTSTR LD HL,WORK+10 CALL PUTSTR CALL CRLF LD A,(WORK) ;check file attributes LD HL,BINFIL CP 0D3H ;check binary file JR Z,LBL03 LD HL,ASCFIL CP 0EAH ;check ascii file JR Z,LBL03 LD HL,MACFIL CP 0D0H ;check machine code file JR Z,LBL03 ERROR: LD HL,ERRSTR LBL03: CALL PUTSTR CALL TAPIOF RET ;----- put CRLF ----- CRLF: LD HL,STCRLF CALL PUTSTR RET ;----- put string ----- PUTSTR: LD A,(HL) ;get a character from strings CP '$' ;check end of strings RET Z CALL CHPUT ;write a character to CRT INC HL JR PUTSTR ;----- strings data ----- FILNAM: DB 'FILE NAME :$' ASCFIL: DB 'ASCII FILE',0DH,0AH,'$' BINFIL: DB 'BINARY FILE',0DH,0Ah,'$' MACFIL: DB 'BSAVE FILE',0DH,0AH,'$' ERRSTR: DB 'TAPE READ ERROR',0DH,0AH,'$' STCRLF: DB 0DH,0AH,'$' ;----- WORK AREA ----- WORK: DS 16,0 DB '$' ;end of strings END ========================================================================= 3. KEYBOARD INTERFACE Altough the MSX2 keyboard has the same design as that of the MSX1, it is more convenient to use because of the Romand-to-kana translation available for kana input. This chapter describes the keyboard interface of the MSX2. Descriptions of the key aarangement are based on the Japanese keyboard standard; note that data is slightly different for the international MSX versions. 3.1 Key Scanning MSX uses the key matrices as shown in Figure 5.16, Figure 5.17 and Figure 5.17B. The key status can be obtained in real time by examining this key matrix and is available for reading input. Scanning the key matrix is done by the following BIOS routine. * SNSMAT (0141H/MAIN) ................. reads the specified line of the key matrix Input: A <-- key matrix line to be read (0 to 10) Output: A <-- status of the specified line of the key matrix (when pressed, the bit of the key is 0) Function: specifies a line of the key matrix shown in Figure 5.16, Figure 5.17 or Figure 5.17B and stores its status in the A register. The bit corresponding with the key being pressed is "0", and "1" for the key not being pressed. Figure 5.16 MSX USA version key matrix MSB LSB 7 6 5 4 3 2 1 0 ----------------------------------------------------------------- 0 | B | L | | / | 1 | S | X | , | |-------+-------+-------+-------+-------+-------+-------+-------| 1 | V | J | = | ` | Q | A | C | N | |-------+-------+-------+-------+-------+-------+-------+-------| 2 | G | 8 | 0 | ] | W | F | Z | M | |-------+-------+-------+-------+-------+-------+-------+-------| 3 | T | I | ~ | ; | 2 | D | U | \ | |-------+-------+-------+-------+-------+-------+-------+-------| 4 | 6 | K | P | ' | 3 | R | 7 | H | |-------+-------+-------+-------+-------+-------+-------+-------| 5 | 5 | 0 | 9 | [ | 4 | E | Y | . | |-------+-------+-------+-------+-------+-------+-------+-------| 6 | F3 | F2 | F1 | CODE | CAPS | GRAPH | CTRL | SHIFT | |-------+-------+-------+-------+-------+-------+-------+-------| 7 | RETURN| SELECT| BS | STOP | TAB | ESC | F5 | F4 | |-------+-------+-------+-------+-------+-------+-------+-------| 8 | RIGHT | DOWN | UP | LEFT | DEL | INS | HOME | SPACE | ----------------------------------------------------------------- [TEN KEY] ----------------------------------------------------------------- 9 | 4 | 3 | 2 | 1 | 0 | option| option| option| |-------+-------+-------+-------+-------+-------+-------+-------| 10 | . | , | - | 9 | 8 | 7 | 6 | 5 | ----------------------------------------------------------------- Figure 5.17 MSX International version key matrix MSB LSB 7 6 5 4 3 2 1 0 ----------------------------------------------------------------- 0 | B | L |deadkey| / | 1 | S | X | , | |-------+-------+-------+-------+-------+-------+-------+-------| 1 | V | J | ^ | ] | Q | A | C | N | |-------+-------+-------+-------+-------+-------+-------+-------| 2 | G | 8 | 0 | [ | W | F | Z | M | |-------+-------+-------+-------+-------+-------+-------+-------| 3 | T | I | ~ | ; | 2 | D | U | \ | |-------+-------+-------+-------+-------+-------+-------+-------| 4 | 6 | K | P | : | 3 | R | 7 | H | |-------+-------+-------+-------+-------+-------+-------+-------| 5 | 5 | 0 | 9 | @ | 4 | E | Y | . | |-------+-------+-------+-------+-------+-------+-------+-------| 6 | F3 | F2 | F1 | CODE | CAPS | GRAPH | CTRL | SHIFT | |-------+-------+-------+-------+-------+-------+-------+-------| 7 | RETURN| SELECT| BS | STOP | TAB | ESC | F5 | F4 | |-------+-------+-------+-------+-------+-------+-------+-------| 8 | RIGHT | DOWN | UP | LEFT | DEL | INS | HOME | SPACE | ----------------------------------------------------------------- [TEN KEY] ----------------------------------------------------------------- 9 | 4 | 3 | 2 | 1 | 0 | option| option| option| |-------+-------+-------+-------+-------+-------+-------+-------| 10 | . | , | - | 9 | 8 | 7 | 6 | 5 | ----------------------------------------------------------------- Figure 5.17B MSX European version key matrix MSB LSB 7 6 5 4 3 2 1 0 ----------------------------------------------------------------- 0 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |-------+-------+-------+-------+-------+-------+-------+-------| 1 | ; | ] | [ | \ | = | - | 9 | 8 | |-------+-------+-------+-------+-------+-------+-------+-------| 2 | B | A | accent| / | . | , | ` | ' | |-------+-------+-------+-------+-------+-------+-------+-------| 3 | J | I | H | G | F | E | D | C | |-------+-------+-------+-------+-------+-------+-------+-------| 4 | R | Q | P | O | N | M | L | K | |-------+-------+-------+-------+-------+-------+-------+-------| 5 | Z | Y | X | W | V | U | T | S | |-------+-------+-------+-------+-------+-------+-------+-------| 6 | F3 | F2 | F1 | CODE | CAPS | GRAPH | CTRL | SHIFT | |-------+-------+-------+-------+-------+-------+-------+-------| 7 | RETURN| SELECT| BS | STOP | TAB | ESC | F5 | F4 | |-------+-------+-------+-------+-------+-------+-------+-------| 8 | RIGHT | DOWN | UP | LEFT | DEL | INS | HOME | SPACE | ----------------------------------------------------------------- [TEN KEY] ----------------------------------------------------------------- 9 | 4 | 3 | 2 | 1 | 0 | option| option| option| |-------+-------+-------+-------+-------+-------+-------+-------| 10 | . | , | - | 9 | 8 | 7 | 6 | 5 | ----------------------------------------------------------------- List 5.4 Use of the key scanning routine ================================================================= ;******************************************************** ; ; List 5.4 scan key-matrix and display it ; ;******************************************************** ; CHPUT EQU 00A2H BREAKX EQU 00B7H POSIT EQU 00C6H SNSMAT EQU 0141H ORG 0B000H ;----- program start ----- Note: read key matrix and display key pattern. SCAN: LD C,0 ;C := line of key matrix SC1: LD A,C CALL SNSMAT ;Read key matrix LD B,8 LD HL,BUF ;HL : = buffer address SC2: LD D,'.' RLA ;Check bit JR C,SC3 LD D,'#' SC3: LD (HL),D ;store '.' or '#' to buffer INC HL DJNZ SC2 LD H,05H ;x := 5 LD L,C ;y := C+1 INC L CALL POSIT ;set cursor position LD B,8 ;put out bit patterns to CRT LD HL,BUF SC4: LD A,(HL) CALL CHPUT INC HL DJNZ SC4 CALL BREAKX ;check Ctrl-STOP RET C INC C ;line No. increment LD A,C CP 09 JR NZ,SC1 JR SCAN ;----- work area ----- BUF: DS 8 END ================================================================= 3.2 Character Input MSX scans the key matrix every 1/60 second using the timer interrupt and, when a key is pressed, stores the character code in the keyboard buffer as shown in Figure 5.18. Key input to MSX is generally done by reading this keyboard buffer. Figure 5.18 Keyboard ring buffer +----------------------------------<----------------------------------------+ | KEYBUF (FBF0H, 40) | | --------------------------------------/ /-------------------------------- | +>| D | E | F | G | | | \ \ | | | A | B | C |-+ --------------------------------------/ /-------------------------------- ^ ^ | | [PUTPNT] [GETPNT] GETPNT (F3FAH, 2) points to the next character to be obtained in CHGET routine. PUTPNT (F3F8H, 2) points to the next location for the character to be put when the keyboard is pressed next time. BIOS routines having functions for key input using this keyboard buffer and functions related to it are described below. Inhibiting the timer interrupt renders them useless, of course. * CHSNS (009CH/MAIN) .................. checks the keyboard buffer Input: --- Output: Z flag = ON when the buffer is empty Function: examines whether any characters remain in the keyboard buffer and sets the Z flag when the buffer is empty. * CHGET (009FH/MAIN) .................. one character input from the keyboard buffer Input: --- Output: A <-- character code Function: reads one character from the keyboard buffer and stores it in the A register. When the buffer is empty, it displays the cursor and waits for a key input. While a key input is waited for, the CAP lock, KANA lock, and Roman-to-kana translation lock are valid. The related work area is listed below. In the list, since SCNCNT and REPCNT are initialised after the execution of CHGET routine, this area should be set at each CHGET call to change the interval of the auto-repeat. Work area CLIKSW (F3DBH, 1) key click sound (0 = OFF, others = ON) SCNCNT (F3F6H, 1) key scanning interval (1, normally) REPCNT (F3F7H, 1) delay until beginning auto-repeat (50, normally) CSTYLE (FCAAH, 1) figure of the cursor (0 = block, others = underline) CAPST (FCABH, 1) CAPS lock (0 = OFF, others = ON) DEADST (FCACH, 1) dead key lock 0 = on preceding dead key 1 = dead key 2 = shifted dead key 3 = code dead key 4 = code shift dead key * KILBUF (0156H/MAIN) ................. empty the keyboard buffer Input: --- Output: --- Function: empties the keyboard buffer. List 5.5 Use of one character input routine ================================================================= ;******************************************************** ; ; List 5.5 get key code ; ; this routine doesn't wait for key hit ; ;******************************************************** ; CHSNS EQU 009CH ;check keyboard buffer CHGET EQU 009FH ;get a character from buffer CHPUT EQU 00A2H ;put a character to screen BREAKX EQU 00B7H ;check Ctrl-STOP KILBUF EQU 0156H ;clear keyboard buffer REPCNT EQU 0F3F7H ;time interval until key-repeat KEYBUF EQU 0FBF0H ;keyboard buffer address ORG 0B000H ;----- prgram start ----- Note: Real-time input using CHGET KEY: CALL CHSNS ;check keyboard buffer JR C,KEY1 LD A,1 LD (REPCNT),A ;not to wait until repeat CALL CHGET ;get a character (if exists) JR KEY2 KEY1: LD A,'-' ;A := '-' KEY2: CALL CHPUT ;put the character CALL KILBUF ;clear keyboard buffer CALL BREAKX ;check Ctrl-STOP JR NC,KEY END ================================================================= * CNVRCHR (00AB/MAIN) ................. graphic character operation Input: A <-- character code Output: A <-- translated graphic character (normal characters are not translated) CY flag = OFF (input was the graphic header byte 01H) CY flag = ON, Z flag = ON (input was the graphic character and was translated) CY flag = ON, Z flag = OFF (input was the normal character and was not translated) Function: executing CNVCHR after CHGET causes the graphic character to be translated to one byte code as shown in Figure 5.19 and causes other character not to be translated and to be returned. Since the graphic character is represented by irregular 2-byte code with the graphic header byte (01H), annoying procedures are required for the character operations; this routine makes it somewhat easy. Figure 5.19 Graphic character translation chart ------------------------------------------------------------- | Before | After | Before | After | | conversion | conversion | conversion | conversion | |-----------------------------+-----------------------------| | | 0150H --> 50H | | 0141H --> 41H | 0151H --> 51H | | 0142H --> 42H | 0152H --> 52H | | 0143H --> 43H | 0153H --> 53H | | 0144H --> 44H | 0154H --> 54H | | 0145H --> 45H | 0155H --> 55H | | 0146H --> 46H | 0156H --> 56H | | 0147H --> 47H | 0157H --> 57H | | 0148H --> 48H | 0158H --> 58H | | 0149H --> 49H | 0159H --> 59H | | 014AH --> 4AH | 015AH --> 5AH | | 014BH --> 4BH | 015BH --> 5BH | | 014CH --> 4CH | 015CH --> 5CH | | 014DH --> 4DH | 015DH --> 5DH | | 014EH --> 4EH | 015EH --> 5EH | | 014FH --> 4FH | 015FH --> 5FH | ------------------------------------------------------------- * PINLIN (00AEH/MAIN) ................. one line input Input: --- Output: HL <-- F55DH [F55EH] <-- input string (the end of te line is represented by 00H) CY flag <-- terminated by STOP=ON, terminated by RETURN=OFF function: stores input string in the line buffer BUF (F55EH). All functions of the screen editing are available at the string input. Pressing RETURN or STOP causes the input to be finished. The work area is listed below. Work area BUF (F55EH, 258) the line buffer where the string is stored LINTTB (FBB2H, 24) 00H when the one physiscal line is the succession of the line above * INLIN (00B1H/MAIN) .................. one line input (prompt available) Input: --- Output: same as PINLIN Function: stores input string in the line buffer BUF (F55EH), as PINLIN routine. Note that the portion before the cursor location at the time when the routine begins to execute is not received. List 5.6 shows the difference between PINLIN and INLIN. List 5.6 Difference between INLIN and PINLIN ================================================================= ;************************************************ ; ; List 5.6 INLIN and PINLIN ; ;************************************************ ; CHPUT EQU 00A2H INLIN EQU 00B1H PINLIN EQU 00AEH KILBUF EQU 0156H BUF EQU F55EH ORG 0B000H ;----- program start ----- LD HL,PRMPT1 CALL PUTMSG ;put prompt message CALL INLIN ;use INLIN routine LD HL,BUF CALL PUTMSG LD HL,PRMPT2 CALL PUTMSG ;put prompt message CALL PINLIN ;use PINLIN routine LD HL,BUF CALL PUTMSG RET ;----- put a string ----- PUTMSG: LD A,(HL) CP '$' RET Z CALL CHPUT INC HL JR PUTMSG ;----- string data ----- PRMPT1: DB 0DH,0AH,'INLIN:$' PRMPT2: DB 0DH,0AH,'PINLIN:$' END ================================================================= 3.3 Function Keys MSX has ten function keys, which can be defined by the user at will. A 16 byte work area is allocated for the definition of each key. The following list shows their addresses. FNKSTR (F87FH, 16) ............ F1 key definition address + 10H (F88FH, 16) ............ F2 key definition address + 20H (F89FH, 16) ............ F3 key definition address + 30H (F8AFH, 16) ............ F4 key definition address + 40H (F8BFH, 16) ............ F5 key definition address + 50H (F8CFH, 16) ............ F6 key definition address + 60H (F8DFH, 16) ............ F7 key definition address + 70H (F8EFH, 16) ............ F8 key definition address + 80H (F8FFH, 16) ............ F9 key definition address + 90H (F90FH, 16) ............ F10 key definition address Pressing a function key causes the string defined in that key to be stored in [KEYBUF]. The end of the string is indicated by 00H and a maximum of 15 keystrokes can be defined for one function key (definitions longer than 16 keystrokes are defined over more than one function key definition area). To restore the initial settings of the function keys, use the following BIOS routine. * INIFNK (003EH/MAIN) ................. initialize function keys Input: --- Output: --- Function: restores the function key definition to the setting when BASIC starts. 3.4 STOP Key During Interrupts CHGET, the one-character input routine described in 3.3, determines the pressed key in the timer interrupt routine. Thus, when the timer interrupt is inhibited, such as during cassette data I/O, pressed keys cannot be detected. By using the BIOS routine described below, the CTRL key + STOP key combination can be detected even when interrupts are inhibited. * BREAKX (00B7H/MAIN) ................. CTRL + STOP detection Input: --- Output: CY flag = ON, when CTRL + STOP is pressed Function: scans keys and decides whether CTRL key and STOP key are pressed at the same time. When both are pressed, this routine sets "1" to the CY flag and returns. Otherwise, it resets "0" to the CY flag and returns. This routine is available while interrupts are inhibited. 4. PRINTER INTERFACE This section describes how to access the MSX printer interface from assembly language. The information described here is helpful if the printer is going to be used to print bit image graphics. 4.1 Print Interface Overview The printer interface is supported by BIOS and BASIC. MSX drives the printer through an 8-bit parallel output port and uses a handshaking method with BUSY and STROBE signals. The standard connector is also defined (Amphenol 14-pin, female side to the machine). Figure 5.20 shows the signal lines. Figure 5.20 Printer interface Printer interface pin connections ------------------------------------------------------------------- \ ------------------------------------------- / \ | (7) | (6) | (5) | (4) | (3) | (2) | (1) | / \ --------------------------------------------------- / \ | | / \ --------------------------------------------------- / \ | (14)| (13)| (12)| (11)| (11)| (10)| (9) | / \ ------------------------------------------- / --------------------------------------------------- (1) ........... STROBE* (2) to (9) .... Data (b0 to b7) (11) .......... BUSY (14) .......... BGND ------------------------------------------------- I/O port (91H) | X | X | X | X | X | X | X | X | ------------------------------------------------- Data ------------------------------------------------- I/O port (90H; at WRITE) | . | . | . | . | . | . | . | X | ------------------------------------------------- ^ | STROBE* (send data when "0") ----+ ------------------------------------------------- I/O port (90H; at READ) | . | . | . | . | . | . | X | . | ------------------------------------------------- ^ 0: Printer READY | ---+ 1: Printer BUSY 4.2 Output to the MSX Standard Printer If data is sent from MSX to the printer, the action depends on whether the printer receiving the data is of the MSX standard. The use of MSX standard printers is described in this section. Descriptions about other printers are in the next section. An MSX standard printer can print any character that can be displayed on the screen. Special graphic characters corresponding to character codes n = 01H to 1FH can be also printed by sending the code 40H + n after the graphic character header (01H). In addition to these, the control codes shown in Table 5.4 can be used with MSX standard printers (see the manual of the printer for controlling a printer which has other functions such as printing Chinese characters). To feed lines in MSX standard printers, send 0DH and 0AH successively. To print the bit image, send nnnn bytes data, where nnnn means four decimal figures, after the escape sequence ESC + "Snnnn". Note that, MSX has a function to transform the tab code (09H) to the adequate number of space codes (20H) for printers not having a tab function. This transformation is normally done. To print a bit image which includes the value 09H correctly, change the following work area. * RAWPRT (F418H, 1) ................... replaces a tab by spaces when the contents are 00H, othereise not. Table 5.4 Control codes of the printer ----------------------------------------------------------------------------- | code | function | |-----------------+---------------------------------------------------------| | 0AH | line feed | |-----------------+---------------------------------------------------------| | 0CH | form feed | |-----------------+---------------------------------------------------------| | 0DH | carriage return | |-----------------+---------------------------------------------------------| | ESC + "A" | normal line spacing | | | (spaces between lines; characters are read easily) | |-----------------+---------------------------------------------------------| | ESC + "B" | line spacing for graphics (no space between lines) | |-----------------+---------------------------------------------------------| | ESC + "Snnnn" | bit image printing | ----------------------------------------------------------------------------- 4.3 Access to the printer To send output to the printer, the following BIOS routines are offered. * LPTOUT (00A5H/MAIN) Input: A register <-- character code Output: CY flag = ON at abnormal termination Function: sends a character specified by the A register to the printer. * LPTSTT (00A8/MAIN) Input: --- Output: A register <-- printer status Function: examines the current printer status. After calling this routine, the printer can be used when the A register is 255 and the Z flag is 0; when the A register is 0 and the Z flag is 1, the printer cannot be used. * OUTDLP (014DH,MAIN) Input: A register <-- character code Output: CY flag = ON at abnormal termination Function: sends a character specified by the A register to the printer. Differences between this routine and LPTOUT routine is as following: * prints corresponding number of spaces for TAB code * transforms hiragana to katakana for printers other than MSX standard * returns Device I/O error at abnormal termination 5. UNIVERSAL I/O INTERFACE As described in section 1, the PSG used by MSX has two 8-bit I/O ports, port A and port B, in addition to the sound output function. In MSX, these two ports are connected to the universal I/O interface (joystick port) and are used to exchange data with the joystick or the paddle (see Figure 5.21). Various devices to be connected to this universal I/O interface have the necessary BIOS routine in ROM, so they are easily accessbile. In this section, the funtion of each I/O device and the method for accessing with BIOS routines are described. Figure 5.21 Universal I/O interface Universal input/output interface -1 ----------------------------------------- | | | (1) (2) (3) (4) (5) -+- +5V Switching signal <---+ | | (6) | (7) | (8) | (9) -----+- GND (to port B:b6) | | | | | | | | | | | ----:---:---:---:---:---:---:------------ | | | | | | | | | | | | | | +---:--> To port B:b4 ------------------------- | | | | | | | | | | +---+---+---+---+-------+--------------------| | | | Switcher |--+ +---+---+---+---+-------+--------------------| | | | | | | | | | | | | | | +---:--> To port B:b5 ------------------------- | | | | | | | | | | | | | ----:---:---:---:---:---:---:------------ (1) (2) (3) (4) (6) (7) | | | | | | | | | | | | | | | | | | (1) (2) (3) (4) (5) -+- +5V +-------------------------+ | (6) (7) (8) (9) -----+- GND | | | V ----------------------------------------- To port A:b0 to b5 Universal input/output interface -2 5.1 Functions of the Ports Two I/O ports of PSG are used as shown in Figure 5.22. Figure 5.22 (A) Functions of PSG port A Port A (PSG#14) ------------------------------------------------- | b7 | . | b5 : b4 : b3 : b2 : b1 : b0 | ------------------------------------------------- | | | | | | | --+ | | | | | | +--> 1st terminal | connected | | | | | +--------> 2nd terminal | to | | | | +--------------> 3rd terminal | universal | | | +--------------------> 4th terminal | I/O | | +--------------------------> 6th terminal | interface | +--------------------------------> 7th terminal | | --+ +-----------------------------------> Data input from the cassette tape Figure 5.22 (B) Functions of PSG port B Port B (PSG#15) ------------------------------------------------- | b7 | b6 | b5 | b4 | b3 | b2 | b1 | b0 | ------------------------------------------------- | | | | | | | | | | | | +-----+-----+-----+--> Unused | | | | | | | +---> Connected to 8th terminal of univ. I/O interface 1 | | +---------> Connected to 8th terminal of univ. I/O interface 2 | | | +---> 0: b0-b5 of port A to be connected to univ. I/O interface 1 | 1: b0-b5 of port A to be connected to univ. I/O interface 2 | +---------> 0: Arabic or kana mode display lamp on 1: Arabic or kana mode display lamp off 5.2 Joystick Use Figure 5.23 shows the joystick circuit. As the circuit shows, sending "0" to the 8th terminal and reading the 1st to 4th and 6th to 7th terminals enable information about the stick and the trigger buttons to be obtained. However, it is advisable to use BIOS for accessing the joystick, in order to give portability to the program. figure 5.23 Joystick circuit \ (1) O---------------o o------------+ ............. Front | \ | (2) O---------------o o------------+ ............. Back | \ | (3) O---------------o o------------+ ............. Left | \ | (4) O---------------o o------------+ ............. Right | | \ | (6) O---------------o o------------+ ............. Trigger A | \ | (7) O---------------o o------------+ ............. Trigger B | | (8) O-------------------------------+ The following BIOS routines are offered for accessing the joystick. These routines have similar functions to the STICK function and STRIG function of BASIC. The status of the cursor keys or the space bar, in addition to the joystick, can be read in real time. * GTSTCK (00D5H/MAIN) ................. read joystick Input: A <-- joystick number (0 = cursor key, 1 and 2 = joystick) Output: A <-- direction of joystick or cursor key Function: returns the current status of the joystick or the cursor keys in the A register. The value is the same as the STICK function in BASIC. * GTTRIG (00D8H/MAIN) ................. read trigger button Input: A <-- trigger button number (0 = space bar, 1 and 2 = trigger button A, 3 and 4 = trigger button B) Output: A <-- status of trigger button or space bar (0FFH = pressed, 00H = released) Function: returns the current status of the trigger buttons or the space bar in the A register. The value is 0FFH when the trigger is pressed, otherwise it is 0. List 5.7 Joystick use ================================================================= ;************************************************ ; ; List 5.7 Joystick and trigger access ; ;************************************************ ; CHPUT EQU 00A2H BREAKX EQU 00B7H GTSTCK EQU 00D5H GTTRIG EQU 00D8H ORG 0D00H ;----- program start ----- Note: display joystick status STICK: LD A,1 ;choose joystick 1 CALL GTSTCK ;read joystick status LD (WK1),A LD A,1 ;choose joystick 1 CALL GTTRIG ;read trigger status OR A JR Z,STCK1 LD HL,WDON ;trigger ON JR STCK2 STCK1: LD HL,WDOFF ;trigger OFF STCK2: CALL PUTSTR LD A,(WK1) OR A JR Z,BRKCH0 ;do not use joystick LD C,0 STCK3: DEC A JR NZ,STCK4 INC C JR STCK3 STCK4: SLA C ;C := C*16 SLA C SLA C SLA C LD B,0 ;Accounting Strings data address LD HL,WDSTK ADD HL,BC CALL PUTSTR BRKCH0: LD A,0DH ;put carriage return CALL CHPUT ;code := 0DH BRKCHK: CALL BREAKX ;break check RET C JR STICK ;----- put strings to screen ----- PUTSTR: LD A,(HL) CP '$' RET Z INC HL CALL CHPUT JR PUTSTR ;----- string area ----- WDON: DB 'Trigger ON: $' WDOFF: DB 'Trigger OFF: $' WDSTK: DB 'UP only ',0DH,0AH,'$' DB 'Up and Right ',0DH,0AH,'$' DB 'Right only ',0DH,0AH,'$' DB 'Right & Down ',0DH,0AH,'$' DB 'Down only ',0DH,0AH,'$' DB 'Down and Left',0DH,0AH,'$' DB 'Left only ',0DH,0AH,'$' DB 'Left and Up ',0DH,0AH,'$' WK1: DW 0 END ================================================================= 5.3 Paddle Use Figure 5.24 shows the paddle circuit. Sending a pulse to the 8th terminal causes the single stable multi-vibrator to generate a pulse with a specified interval. This interval depends on the value of the variable register which can range from 10 to 3000 microseconds (0.01 to 3.00 ms). Measuring the pulse length enables the value in the variable register and the turning angle to be obtained. Figure 5.24 Paddle circuit --+-- | <_ _> 150KOhm Variable Resistor < | 0.04 uF | +--| |---+ | | ---+--------+--- | | |\ | | | \ | | (8) -----| >O----O| A Q |------------- (1) (For 2, 3, 4, 6, or 7, | / | | a similar circuit |/ | | would apply) | | | | +----------| B | | | | | | | (One-shot trigger IC, LS123 compatible) | | | +5V | ---------------- --+-- | O | | | +-----+-----------------+ ____ : : Input to 8 ________: :_____________________________________ _________________________________ : : Output to 1 ________: :________ |<------- 10 us to 3 ms ------->| BIOS routines for accessing the paddle are described below. * GTPDL (00DEH/MAIN) .................. read paddle information Input: A <-- paddle number (1 to 12) Output: A <-- turning angle (0 to 255) Function: examines the status of the paddle specified in the A register and returns the result in the A register. 5.4 Use of Touch Panel, Light Pen, Mouse, and Track Ball The touch panel, light pen, mouse, and track ball (cat) are accessible using the same BIOS routine. This routine is described below. * GTPAD (00DBH/MAIN) .................. access to various I/O devices Input: A <-- device ID (0 to 19) Output: A <-- objective information Function: obtains various information as shown in Table 5.5 according to the value specified in the A register. This is the same as the PAD function of BASIC. "XXX1" in the table means the "XXX" device connected to the universal I/O interface 1; "XXX2" means the one connected to the universal I/O interface #2. Table 5.5 GTPAD BIOS Function -------------------------------------------------------------------------- | Device ID | Device specified | Information returned | --------------+--------------------+-------------------------------------| | 0 | | 0FFH when touching panel surface, | | | | 00H when not | |-------------| |-------------------------------------| | 1 | | X-coordinate (0 to 255) | |-------------| Touch panel 1 |-------------------------------------| | 2 | | Y-coordinate (0 to 255) | |-------------| |-------------------------------------| | 3 | | 0FFH when button is pressed, | | | | 00H when not | |-------------+--------------------+-------------------------------------| | 4 | | | |-------------| | | | 5 | | | |-------------| Touch panel 2 | Same as above | | 6 | | | |-------------| | | | 7 | | | |-------------+--------------------+-------------------------------------| | 8 | | 0FFH: valid data, | | | | 00H: invalid data | |-------------| |-------------------------------------| | 9 | | X-coordinate (0 to 255) | |-------------| Light pen |-------------------------------------| | 10 | | Y-coordinate (0 to 255) | |-------------| |-------------------------------------| | 11 | | 0FFH when switch is pressed, | | | | 00H when not | |-------------+--------------------+-------------------------------------| | 12 | | Always 0FFH | | | | (used to request for input) | |-------------| |-------------------------------------| | 13 | Mouse 1 or | X-coordinate (0 to 255) | |-------------| track ball 1 |-------------------------------------| | 14 | | Y-coordinate (0 to 255) | |-------------| |-------------------------------------| | 15 | | Always 00H | | | | (no meaning) | |-------------+--------------------+-------------------------------------| | 16 | | | |-------------| | | | 17 | Mouse 2 or | | |-------------| track ball 2 | Same as above | | 18 | | | |-------------| | | | 19 | | | -------------------------------------------------------------------------- Note 1: Though information of the coordinate of the light pen (A = 9, 10) and the switch (A = 11) are read at the same time when BIOS is called with A = 8, other values are valid only when the result is 0FFH. In the case that the result of BIOS which is called with A = 8 is 00H, the coordinate values and the status of the switch contained after that are meaningless. Note 2: Mouse and track ball are automatically distinguished. Note 3: To obtain the coordinate value of the mouse or the track ball, do the input request call (A = 12 or A = 16), then execute the call to obtain the coordinate value actually. In this case, the interval of these two calls must be minimized as possible. Too much interval between the input request and the coordinate input causes the obtained data to be unreliable. Note 4: To obtain the status of the trigger button of the mouse or the trigger button of the track ball, use GTTRIG (00D8H/MAIN), not GTPAD routine. List 5.8 Touch panel use ================================================================= ;************************************************ ; ; List 5.8 touch pad access ; ;************************************************ ; BREAKX EQU 00B7H GTPAD EQU 00D8H WRTVRM EQU 004DH ORG 0B000H ;----- program start ----- Note: Displays "*" at position specified by touch pad. PAD: XOR A ;check sense CALL GTPAD OR A JR NZ,PAD1 LD A,3 CALL GTPAD ;break check OR A RET NZ JR PAD PAD1: LD A,1 ;get X axis CALL GTPAD SRL A ;A := A/8 SRL A SRL A LD (WORK),A ;reserve X axis LD A,2 ;get Y axis CALL GTPAD LD L,A ;HL := Y data (0-255) LD H,0 LD C,A LD B,0 ADD HL,BC ;HL := HL*3 (HL := 0-767) ADD HL,BC LD A,L AND 11100000B LD L,A LD A,(WORK) ADD A,L LD L,A LD BC,1800H ;VRAM start address ADD HL,BC LD A,2AH CALL WRTVRM ;write VRAM LD A,3 CALL GTPAD ;break check OR A RET NZ JR PAD ;----- work area ----- WORK: DW 0 ;work END ================================================================= List 5.9 Mouse and track ball use ================================================================= ;************************************************ ; ; List 5.9 mouse and track ball access ; ;************************************************ ; GTPAD EQU 00DBH WRTVRM EQU 004DH RDVRM EQU 004AH BREAKX EQU 00B7H ORG 0D000H ;----- program start ----- Note: Displays "*" at position specified by mouse or track ball. TEST: CALL VADR ;Put old data LD A,(WKOLD) CALL WRTVRM LD A,12 CALL GTPAD ;Request mouse/track ball data LD A,13 CALL GTPAD ;Read X val. LD (WKXVAL),A LD A,14 CALL GTPAD ;Read Y val. LD (WKYVAL),A LD A,(WKX) LD B,A LD A,(WKXVAL) ADD A,B CP 245 ;X<0? JR C,TEST01 XOR A ;X=0 JR TEST02 TEST01: CP 32 ;X>31? JR C,TEST02 LD A,31 TEST02: LD (WKX),A LD A,(WKY) LD B,A LD A,(WKYVAL) ADD A,B CP 245 ;Y<0? JR C,TEST03 XOR A ;Y=0 JR TEST04 TEST03: CP 24 ;Y>23? JR C,TEST04 LD A,23 TEST04: LD (WKY),A CALL VADR CALL RDVRM ;Read old data LD (WKOLD),A CALL VADR LD A,2AH CALL WRTVRM ;Put cursor ("*"). CALL BREAKX ;Break check RET C CALL WAIT JR TEST VADR: LD A,(WKY) ;Make SCREEN Address: LD H,A ; From X,Y axis on WORK AREA LD L,0 ; To Hl reg. SRL H RR L SRL H RR L SRL H RR L LD A,(WKX) ADD A,L ; Y=32+X LD L,A LD BC,1800H ; VRAM start address ADD HL,BC RET WAIT: LD A,0 ;WAIT routine WLP1: INC A LD B,(IX+0) LD B,(IX+0) LD B,(IX+0) JR NZ,WLP1 RET ;----- data ----- WKX: DB 10 ;X axis WKY: DB 10 ;Y axis WKOLD: DB 0 ;Character code on (X,Y) WKXVAL: DB 0 ;X variable WKYVAL: DB 0 ;Y variable END ================================================================= 6. CLOCK AND BATTERY-POWERED MEMORY MSX2 uses a CLOCK-IC to for its timer function. Since this IC is battery-powered, it remains active even after MSX2 is turned off. MSX2 uses a small amount of RAM inside to set the PASSWORD or to set the screen mode at startup automatically, in addition to the CLOCK functions. 6.1 CLOCK-IC Functions This IC has the following three functions: * CLOCK function - set/read the settings of "year, month, day, day of week, hour, minute, second" - for the expression of time, 24-hour clock/12-hour clock available - for months, months of 31 days and of 30 days are distinguished (leap years are also recognised) * Alarm function - when the time for alarm is set, CLOCK generates signals at that time. - the time for alarm is set as "XXday XXhour XXminute". * Battery-powered memory function - has 26 sets of 4-bit memory, and can be battery-powered. - MSX2 stores the following data in this memory: 1. adjustment value of CRT display width and height 2. initial values of SCREEN, WIDTH, colour 3. BEEP tone and volume 4. title screen colour 5. country code 6. password --+ 7. BASIC prompt | (one of 6 to 8) 8. title caption --+ 6.2 Structure of the CLOCK-IC The CLOCK-IC has four blocks inside as shown in Figure 5.25. Each block consists of 13 sets of 4-bit registers, which are specified by addresses from 0 to 12. In addition, it has three 4-bit registers for selecting the block or controlling functions; they are specified by the addresses from 13 to 15. The registers inside the block (#0 to #12) and the MODE register (#13) can be read from and written to. The TEST register (#14) and RESET register (#15) can only be written to. Figure 5.25 Clock IC structure BLOCK 0 BLOCK 1 BLOCK 2 BLOCK 2 (CLOCK) (ALARM) (RAM-1) (RAM-2) ---------------- ---------------- ---------------- ---------------- | Seconds (the | | | | | | | 0 | 1st decimal | | ________ | | | | | | place) | | | | | | | |--------------| |--------------| |- -| |- -| | Seconds (the | | | | | | | 1 | 2nd decimal | | ________ | | | | | | place) | | | | | | | |--------------| |--------------| |- -| |- -| . | . | | . | | Any data | | Any data | . | . | | . | | | | | . | . | | . | | | | | . | . | | . | | | | | . | . | | . | | | | | |--------------| |--------------| |- -| |- -| | Year (the | | | | | | | 12| 2nd decimal | | ________ | | | | | | place) | | | | | | | ---------------- ---------------- ---------------- ---------------- :<-- 4 bits -->: :<-- 4 bits -->: :<-- 4 bits -->: :<-- 4 bits -->: ---------------- 13 | MODE | |--------------| --+ 14 | TEST | | |--------------| |-- Write only 15 | RESET | | ---------------- --+ :<-- 4 bits -->: 6.3 MODE Register Functions The MODE register has the following 3 functions: * Selecting block To read from or write to registers from #0 to #12, select the block to be used and then access the objective address. The 2 low order bits of the MODE register are used to select the block. Registers from #13 to #15 are accessible whichever block is selected. * Alarm output ON/OFF To switch the alarm input ON/OFF, use bit 2 of the MODE register. Since the standard MSX2 does not support the alarm, modifying this bit causes nothing to happen in general. * Terminating CLOCK count By writing "0" in bit 3 of the MODE register, the count in seconds is stopped (the stages before the seconds are not stopped) and the clock function is terminated. By writing "1" in bit 3, the count is resumed. Figure 5.26 MODE register functions B3 B2 B1 B0 --------------------- | TE | AE | M1 : M0 | MODE register (#13) --------------------- | | | 00: select block 0 | | | 01: select block 1 | | +----> 10: select block 2 | | 11: select block 3 | | | +------------> 0: alarm output OFF | 1: alarm output ON | +-----------------> 0: CLOCK count stop (in seconds) 1: CLOCK count start 6.4 TEST Register functions The TEST register (#14) is used to increment the upper counter quickly and to confirm that date and time carries are done correctly. Setting "1" in each bit of the register, the pulse of 2^14 (=16384)[Hz] is directly set in day, hour, minute, and second counters. Figure 5.27 TEST register functions B3 B2 B1 B0 --------------------- | T3 | T2 | T1 | T0 | TEST register (#14) --------------------- | | | | | Hours | Seconds ........ the location for the pulse to be placed Day Minutes 6.5 RESET Register Functions The RESET register (#15) has the following functions: * Resetting the alarm Setting "1" in bit 0 causes all alarm registers to be reset to 0. * Setting the seconds Setting "1" in bit 1 causes the stage before the seconds to be reset. Use this function to set the seconds correctly. * Clock pulse ON/OFF Setting "1" in bit 2 turns the 16Hz clock pulse output ON, and setting "0" in bit 3 turns the 1Hz clock pulse output ON. Note that both are not supported by the MSX2 standard. Figure 5.28 RESET register function B3 B2 B1 B0 --------------------- | C1 | C16| CR | AR | RESET register (#15) --------------------- | | | | | | | +--> When "1", all alarm registers are reset | | +-------> When "1", fractions smaller than a second are reset | +------------> When "0", 16[Hz] clock pulse is ON +-----------------> When "0", 1[Hz] clock pulse is ON 6.6 Setting the Clock and Alarm * Setting date and time Block 0 is used to set the clock. Selecting block 0 in the MODE register and writing data in the objective register causes the date and the time to be set. The current time is acquired by reading the contents of the register. See Figure 5.29 for the meaning of the register and its address. Block 1 is used to set the alarm. Note that the time of the alarm can be set only in days, hours, and minutes. Nothing happens, in general, when the time of the clock meets the time of the alarm. In the clock, the year is represented by 2 digits (registers #11 and #12). In MSX-BASIC, the 2 low order digits of the year is represented by adding the offset 80 to this value. For example, after setting register #11 to 0 and register #12 to 0, the year would be 80, as "80/XX/XX", when the date is read by using the GET DATE instruction of BASIC. The day of the week is represented by 0 to 6. This is only a mod 7 counter which is renewed alomg with the date, and the correspondence between the actual day of the week and the number value 0 to 6 is not defined. Figure 5.29 Setting the CLOCK and ALARM block 0 : CLOCK --------------------------------------------------------- | | B3 | B2 | B1 | B0 | |---------------------------+---------------------------| 0 | Seconds | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 1 | Seconds | | | (the 2nd decimal place) | . X X X | |---------------------------+---------------------------| 2 | Minutes | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 3 | Minutes | | | (the 2nd decimal place) | . X X X | |---------------------------+---------------------------| 4 | Hours | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 5 | Hours | | | (the 2nd decimal place) | . . X X | |---------------------------+---------------------------| 6 | Day of | | | the week | . X X X | |---------------------------+---------------------------| 7 | Day | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 8 | Day | | | (the 2nd decimal place) | . . X X | |---------------------------+---------------------------| 9 | Month | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 10 | Month | | | (the 2nd decimal place) | . . . X | |---------------------------+---------------------------| 11 | Year | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 12 | Year | | | (the 2nd decimal place) | X X X X | --------------------------------------------------------- block 1 : ALARM --------------------------------------------------------- | | B3 | B2 | B1 | B0 | |---------------------------+---------------------------| 0 | _________________ | | | | . . . . | |---------------------------+---------------------------| 1 | _________________ | | | | . . . . | |---------------------------+---------------------------| 2 | Minutes | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 3 | Minutes | | | (the 2nd decimal place) | . X X X | |---------------------------+---------------------------| 4 | Hours | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 5 | Hours | | | (the 2nd decimal place) | . . X X | |---------------------------+---------------------------| 6 | Day of | | | the week | . X X X | |---------------------------+---------------------------| 7 | Day | | | (the 1st decimal place) | X X X X | |---------------------------+---------------------------| 8 | Day | | | (the 2nd decimal place) | . . X X | |---------------------------+---------------------------| 9 | _________________ | | | | . . . . | |---------------------------+---------------------------| 10 | 12 or | | | 24 hours | . . . X | |---------------------------+---------------------------| 11 | Leap year | | | counter | . . X X | |---------------------------+---------------------------| 12 | _________________ | | | | . . . . | --------------------------------------------------------- Bits indicated by an "." are always 0 and cannot be modified. * Selecting 12-hour clock/24-hour clock Two clocks can be selected; one is a 24-hour clock which represents one o'clock in the afternoon as 13 o'clock, and the other is a 12-hour clock which represents it as 1 p.m. Register #10 is used to select between them. As shown in Figure 5.30, the 12-hour clock is selected when B0 is "0" and the 24-hour clock when B0 is "1". Figure 5.30 Selecting 12-hour clock/24-hour clock B3 B2 B1 B0 --------------------- | . | . | . | B0 | Register #10 (block 1) --------------------- | +--> 0: 12-hour clock 1: 24-hour clock Figure 5.31 Morning/afternoon flag for 12-hour clock B3 B2 B1 B0 --------------------- | . | . | B1 | X | register #5 (block 0) --------------------- | +-------> 0: before noon 1: after noon * Leap year counter Register #11 of block 1 is a mod 4 counter which is renewed along with the count of the year. When the 2 low order bits of this register are 00H, that is considered as a leap year and 29 days are counted in February. Figure 5.32 Leap year determination B3 B2 B1 B0 --------------------- | . | . | B1 | B0 | Register #11 (block 1) --------------------- | | +----+--> Both bits 0 represents leap year. 6.7 Contents of the Battery-powered Memory Blocks 2 and 3 of the CLOCK-IC are used as the battery-powered 4-bit x 13 memory blocks. MSX2 uses this area as shown below. * Contents of block 2 Figure 5.33 Contents of block 2 | B3 | B2 | B1 | B0 | |-------------------------------------------------------------------| 0 | ID | |-------------------------------------------------------------------| 1 | Adjust X (-8 to +7) | |-------------------------------------------------------------------| 2 | Adjust Y (-8 to +7) | |-------------------------------------------------------------------| 3 | __________ | __________ | Interlace mode | Screen mode | |-------------------------------------------------------------------| 4 | WIDTH value (Lo) | |-------------------------------------------------------------------| 5 | WIDTH value (Hi) | |-------------------------------------------------------------------| 6 | Foreground color | |-------------------------------------------------------------------| 7 | Background color | |-------------------------------------------------------------------| 8 | Border color | |-------------------------------------------------------------------| 9 | Cassette speed | Printer mode | Key click | Key ON/OFF | |---------------------------------+---------------------------------| 10 | BEEP tone | BEEP volume | |---------------------------------+---------------------------------| 11 | __________ | __________ | Title colour | |-------------------------------------------------------------------| 12 | Native code | --------------------------------------------------------------------- * Contents of block 3 Block 3 has three functions, depending on the contents of the ID value (register #0). Figure 5.34 shows the functions. Figure 5.34 Contents of block 3 ID=0: displays the title (within 6 characters) on the initial screen ------------------------------------------------------ 0 | 0 | |----------------------------------------------------| --+ 1 | Lo 1 --+--- 1st character of the title | | | | | | 2 | Hi 1 --+ | | |----------------------------------------------------| | . | . | | . | . | | 6 characters . | . | | |----------------------------------------------------| | 11 | Lo 6 --+--- 6th character of the title | | | | | | 12 | Hi 6 --+ | | ------------------------------------------------------ --+ ID=1: sets the password ------------------------------------------------------ 0 | 1 | |----------------------------------------------------| 1 | Usage ID=1 | | | 2 | Usage ID=2 | | | 3 | Usage ID=3 | |----------------------------------------------------| 4 | Password --+ | | | | 5 | Password | Password data is stored | | |-- compressed in 4bits x 4 bits | 6 | Password | | | | | 7 | Password --+ | |----------------------------------------------------| 8 | Key cartridge flag | |----------------------------------------------------| 9 | Key cartridge value | | | 10 | Key cartridge value | | | 11 | Key cartridge value | | | 12 | Key cartridge value | ------------------------------------------------------ ID=2: sets the prompt on BASIC ------------------------------------------------------ 0 | 2 | |----------------------------------------------------| --+ 1 | Lo 1 --+--- 1st character of the prompt | | | | | | 2 | Hi 1 --+ | | |----------------------------------------------------| | . | . | | . | . | | 6 characters . | . | | |----------------------------------------------------| | 11 | Lo 6 --+--- 6th character of the prompt | | | | | | 12 | Hi 6 --+ | | ------------------------------------------------------ --+ 6.8 Access to the CLOCK-IC The following BIOS routines are offered to access the clock and the battery-powered memory. Since these routines reside in SUB-ROM, they are called by using the inter-slot call. * REDCLK (015FH/SUB) .................. read CLOCK-IC data Input: C <-- CLOCK-IC address (see Figure 5.35) Output: A <-- data obtained (only 4 low order bits valid) Function: reads CLOCK-IC register in the address specified by the C register and stores in the A register. Since the address specification includes the block selection information as shown in Figure 5.35, it is not necessary to set the MODE register and then read the objective register. Figure 5.35 CLOCK-IC register specification method ----------------------------------------- C register | . | . | M1 : M0 | A3 : A2 : A1 : A0 | ----------------------------------------- | | | +---------+-------------------+ Block to be Register selected address * WRTCLK (01F9H/SUB) .................. write CLOCK-IC data Input: C <-- CLOCK-IC address (see Figure 5.35) A <-- data to be written (4 low order bits) Output: --- Function: write the contents of the A register in the CLOCK-IC at the address specified by the C register. The address is specified in the format shown in Figure 5.35 as REDCLK. List 5.10 shows an example of this BIOS routine. List 5.10 Setting the prompt ================================================================= ;************************************************ ; ; List 5.10 set prompt message ; ;************************************************ ; WRTCLK: EQU 01F9H EXTROM: EQU 015FH ORG 0B000H ;----- program start ----- ;Note: Set prompt message for BASIC. START: LD C,00110000B ;address data LD A,2 ;ID := prompt mode CALL WRTRAM ;write to back-up RAM LD B,6 ;loop counter LD HL,STRING ;prompt data L01: LD A,(HL) ;read string data AND 0FH ;A := hi 4 bit INC C ;increment address CALL WRTRAM ;write data to back-up RAM LD A,(HL) RRCA RRCA RRCA RRCA AND 0FH INC C ;increment address CALL WRTRAM ;write low 4 bits INC HL DJNZ L01 RET ;----- write data to back-up RAM ----- WRTRAM: PUSH HL PUSH BC LD IX,WRTCLK CALL EXTROM ;use interslot call POP BC POP HL RET ;----- string data ----- STRING: DB 'Ready?' END =================================================================