A2NoSlotMIDI/LEGACY/MIDIDRVR.SRC.txt
2018-07-16 18:21:02 -04:00

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;-------------------------------------------------------------------------
; APPLE MIDI DRIVER THROUGH ANNUNCIATOR 0
; COPYRIGHT 1998, ERIC RANGELL
;-------------------------------------------------------------------------
; THIS DRIVER IMPLEMENTS ASYNCHRONOUS SERIAL DATA TRANSMISSION
; THROUGH THE APPLE ANNUNCIATOR 0 OUTPUT PORT OF THE GAME CONNECTOR
; USING 32 CYCLES PER BIT TO ACHIEVE A 31.25K MIDI BAUD RATE.
;
; THE OUTPUT IS INITIALIZED TO A HIGH LOGIC VOLTAGE. WHEN IT GOES
; LOW FOR 32 MICROSECONDS, THAT INDICATES THE START BIT OF A MIDI BYTE.
; THEN 8 BYTES OF DATA ARE TRANSMITTED, FOLLOWED BY A HIGH STOP BIT.
; THE DATA BYTES REPRESENT MIDI MESSAGES WHICH CAN BE INTERPRETED BY
; ANY MUSICAL INSTRUMENT THAT IMPLEMENTS MIDI.
;
; ENTRY POINTS:
;
; $9000 = INITIALIZE - TURNS ON ANNUNCIATOR 0 - MUST BE CALLED ONCE
; $9003 = APPLESOFT CALL TO SEND ONE MIDI BYTE. POKE THE BYTE IN $9004.
; $9005 = ASSEMBLY CALL TO SEND ONE MIDI BYTE FROM ACCUMULATOR
; $9008 = APPLESOFT OR ASSEMBLY CALL TO SEND SEVERAL BYTES AT ONCE:
; THE CALLER POPULATES LOCATION $D7 WITH THE NUMBER OF BYTES TO BE
; TRANSMITTED, AND A POINTER IN $CE,CF (LO,HI) WITH THE ADDRESS OF
; THE DATA BYTES, THEN CALLS THE ENTRY POINT "SENDMSG" TO TRANSMIT
; THE MESSAGE.
; $900B = SEND A TEST MESSAGE - C MAJOR CHORD NOTE ONS
; $900E = SEND A TEST MESSAGE - C MAJOR CHORD NOTE OFFS
;-------------------------------------------------------------------------
ORG $9000
;
AN0OFF EQU $C058 ;APPLE ADDRESSES THAT CONTROL ANNUNCIATOR OUTPUTS
AN0ON EQU $C059
AN1OFF EQU $C05A
AN1ON EQU $C05B
AN2OFF EQU $C05C
AN2ON EQU $C05D
AN3OFF EQU $C05E
AN3ON EQU $C05F
;
; CALLER MUST POPULATE THE FOLLOWING TWO ZERO PAGE LOCATIONS FOR SENDMSG:
;
NUMBYTES EQU $D7 ;NUMBER OF BYTES TO BE TRANSMITTED NOW (1-256)
; ;THE VALUE 0 WILL TRANSMIT 256 BYTES.
DATAPTR EQU $CE ;POINTER TO THE BYTES TO BE TRANSMITTED NOW
;---------------------------------------------------------------------------
START JMP INIT ;MAIN ENTRY POINT - INITIALIZES ANNUNCIATORS
SENDFP LDA #$90 ;ENTRY POINT FOR APPLESOFT: POKE BYTE AND CALL
SENDONE JMP XMITONE ;ENTRY POINT FOR TRANSMITTING ONE BYTE FROM ACCUM
SENDMSG JMP XMITMSG ;ENTRY POINT FOR TRANSMITTING A MIDI MESSAGE
ALLNOFF JMP QUIET ;TURN ALL NOTES OFF
TEST1 JMP TESTMSG1 ;SEND TEST MESSAGE 1 - C MAJOR CHORD ON
TEST2 JMP TESTMSG2 ;SEND TEST MESSAGE 2 - C MAJOR CHORD OFF
SAVENBYT DFB $00 ;SAVE AREA FOR NUMBYTES
TEMPA DFB $00
TEMPX DFB $00
;---------------------------------------------------------------------------
INIT BIT AN0ON
RTS
;---------------------------------------------------------------------------
XMITMSG LDA NUMBYTES ;SAVE NUMBER OF BYTES
STA SAVENBYT ;BECAUSE WE WILL CLOBBER IT
LDY #$00 ;Y WILL BE AN INDEX INTO THE DATA AREA
XMITLOOP LDA (DATAPTR),Y ;GET A DATA BYTE
JSR XMITONE
INY ;POINT TO NEXT BYTE
DEC NUMBYTES ;DECREMENT COUNTER
LDA NUMBYTES ;CHECK IF ZERO
BNE XMITLOOP ;LOOP UNTIL DONE SENDING ALL BYTES
LDA SAVENBYT
STA NUMBYTES ;RESTORE ORIGINAL VALUE OF NUMBYTES
RTS
;---------------------------------------------------------------------------
XMITONE STA TEMPA ;SAVE A AND X REGISTERS
STX TEMPX
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT7+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT6+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT5+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT4+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT3+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT2+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT1+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
ASL A ;SHIFT BIT INTO CARRY
TAX ;SAVE CURRENT IMAGE OF DATA BYTE
LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
STA BIT0+1 ;MODIFY THE XMITBITS SUBROUTINE
TXA ;RESTORE ACCUMULATOR
;
JSR XMITBITS ;SEND THE BYTE OUT
LDX TEMPX
LDA TEMPA ;RESTORE X AND A
RTS
;-----------------------------------------------------------------------
XMITBITS BIT AN0OFF ;4 CYCLES - TRANSMIT START BIT - ALWAYS LOW
JSR DELAY22 ;6+22
BIT0 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT1 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT2 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT3 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT4 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT5 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT6 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT7 BIT AN0OFF ;4
JSR DELAY22 ;6+22
BIT AN0ON ;4 ;TRANSMIT STOP BIT - ALWAYS HIGH
JSR DELAY22 ;6+22
RTS
;-----------------------------------------------------------------------
DELAY22 NOP ;WAIT 22 CYCLES
NOP
NOP
NOP
NOP
NOP
NOP
NOP
RTS
;-----------------------------------------------------------------------
TESTMSG1 LDA #7
STA NUMBYTES
LDA #>TESTDAT1
STA DATAPTR
LDA #<TESTDAT1
STA DATAPTR+1
JSR SENDMSG
RTS
;-----------------------------------------------------------------------
TESTMSG2 LDA #7
STA NUMBYTES
LDA #>TESTDAT2
STA DATAPTR
LDA #<TESTDAT2
STA DATAPTR+1
JSR SENDMSG
RTS
;-----------------------------------------------------------------------
QUIET LDA #$90
STA NUMBYTES
LDA #>QUIETMSG
STA DATAPTR
LDA #<QUIETMSG
STA DATAPTR+1
JSR SENDMSG
RTS
;-----------------------------------------------------------------------
CHN MIDIDRVR.SC0