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.
1.3 Tone Generation by 1-bit Sound Port
1.4 Access to 1-bit Sound Port
3.4 STOP Key During Interrupts
4.2 Output to the MSX Standard Printer
5.4 Use of Touch Panel, Light Pen, Mouse, and Track Ball
6. CLOCK AND BATTERY-POWERED MEMORY
6.6 Setting the Clock and Alarm
6.7 Contents of the Battery-powered Memory
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
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.
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.
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.
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.
-----------------------------------------------------------------------------
| 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
-------------------------------------------------
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 ]
----------------------------------------------------------------
| 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 | B4 | 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 |
----------------------------------------------------------------
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).
-------------------------------------------------
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.
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.
-------------------------------------------------
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”.
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.
-------------------------------------------------
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.
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.
-------------------------------------------------
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]
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.
-------------------------------------------------
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
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.
For access the PSG from assembly language programs, several BIOS routines described below are available.
-----------------------------------------------------------------------------
| 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 | |
-----------------------------------------------------------------------------
;************************************************
;
; 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
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.
bit 7 6 5 4 3 2 1 0
-----------------------------------------
| . | | | | | | | |
--+--------------------------------------
| PPI port C (I/O address 0AAH)
|
|
:::::::::::: V
: PSG : ---------
: output :::::::>| MIX |
:::::::::::: ---------
|
V
-----
/ \ Speaker
---------
/ : \
To access to the 1-bit sound port, the following BIOS routine is offered.
;********************************************************
;
; 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
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.
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.
------------------------------------------------
| 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 ,,,<baud rate>
CSAVE "filename",<baud rate>
(<baud rate> is 1 for 1200bps, 2 for 2400 bps)
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.
--------------------------------------------------------------
| 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)
+--+
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.
LSB MSB
-------------------------------------------------------------------------
| 0 | X | X | X | X | X | X | X | X | 1 : 1 |
-------------------------------------------------------------------------
| | | |
+-----+-----------------------------------------------+-----------+
Start bit Data Stop bit
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.
------------------------------------------------------------------
| 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) |
------------------------------------------------------------------
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.
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.
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.
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
The following BIOS routines are offered to access cassette files.
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 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
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 section 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.
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.
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 |
-----------------------------------------------------------------
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 |
-----------------------------------------------------------------
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 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
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.
+----------------------------------<----------------------------------------+
| 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.
Work area:
;********************************************************
;
; 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
-------------------------------------------------------------
| 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 |
-------------------------------------------------------------
Work area:
;************************************************
;
; 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
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.
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.
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.
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.
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.
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
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.
-----------------------------------------------------------------------------
| 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 |
-----------------------------------------------------------------------------
To send output to the printer, the following BIOS routines are offered.
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.
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
Two I/O ports of PSG are used as shown in Figure 5.22.
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
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
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.
\
(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.
;************************************************
;
; 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
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.
--+--
|
<_
_> 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.
The touch panel, light pen, mouse, and track ball (cat) are accessible using the same BIOS routine. This routine is described below.
--------------------------------------------------------------------------
| 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 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 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
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.
This IC has the following three functions:
* (one of 6 to 8)
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.
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 -->:
The MODE register has the following 3 functions:
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.
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.
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.
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
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.
B3 B2 B1 B0
---------------------
| T3 | T2 | T1 | T0 | TEST register (#14)
---------------------
| | | |
| Hours | Seconds ........ the location for the pulse to be placed
Day Minutes
The RESET register (#15) has the following functions:
Setting “1” in bit 0 causes all alarm registers to be reset to 0.
Setting “1” in bit 1 causes the stage before the seconds to be reset. Use this function to set the seconds correctly.
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.
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
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.
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.
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”.
B3 B2 B1 B0
---------------------
| . | . | . | B0 | Register #10 (block 1)
---------------------
|
+--> 0: 12-hour clock
1: 24-hour clock
B3 B2 B1 B0
---------------------
| . | . | B1 | X | register #5 (block 0)
---------------------
|
+-------> 0: before noon
1: after noon
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.
B3 B2 B1 B0
---------------------
| . | . | B1 | B0 | Register #11 (block 1)
---------------------
| |
+----+--> Both bits 0 represents leap year.
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.
| 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 |
---------------------------------------------------------------------
Block 3 has three functions, depending on the contents of the ID value (register #0). Figure 5.34 shows the functions.
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 --+ | |
------------------------------------------------------ --+
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.
-----------------------------------------
C register | . | . | M1 : M0 | A3 : A2 : A1 : A0 |
-----------------------------------------
| | |
+---------+-------------------+
Block to be Register
selected address
List 5.10 shows an example of this BIOS routine.
;************************************************
;
; 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
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.