129 lines
5.3 KiB
Plaintext
129 lines
5.3 KiB
Plaintext
;-------------------------------------------------------------------------
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; APPLE MIDI DRIVER THROUGH ANNUNCIATOR 0
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; COPYRIGHT 1998, ERIC RANGELL
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;-------------------------------------------------------------------------
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; THIS DRIVER IMPLEMENTS ASYNCHRONOUS SERIAL DATA TRANSMISSION
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; THROUGH THE APPLE ANNUNCIATOR 0 OUTPUT PORT OF THE GAME CONNECTOR
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; USING 32 CYCLES PER BIT TO ACHIEVE A 31.25K MIDI BAUD RATE.
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;
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; THE OUTPUT IS INITIALIZED TO A HIGH LOGIC VOLTAGE. WHEN IT GOES
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; LOW FOR 32 MICROSECONDS, THAT INDICATES THE START BIT OF A MIDI BYTE.
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; THEN 8 BYTES OF DATA ARE TRANSMITTED, FOLLOWED BY A HIGH STOP BIT.
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; THE DATA BYTES REPRESENT MIDI MESSAGES WHICH CAN BE INTERPRETED BY
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; ANY MUSICAL INSTRUMENT THAT IMPLEMENTS MIDI.
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;
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;-------------------------------------------------------------------------
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;
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AN0OFF EQU $C058 ;APPLE ADDRESSES THAT CONTROL ANNUNCIATOR OUTPUTS
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AN0ON EQU $C059
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AN1OFF EQU $C05A
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AN1ON EQU $C05B
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AN2OFF EQU $C05C
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AN2ON EQU $C05D
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AN3OFF EQU $C05E
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AN3ON EQU $C05F
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;
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TEMPA DFB $00
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TEMPX DFB $00
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;---------------------------------------------------------------------------
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XMITONE STA TEMPA ;SAVE A AND X REGISTERS
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STX TEMPX
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT7+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT6+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT5+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT4+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT3+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT2+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT1+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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ASL A ;SHIFT BIT INTO CARRY
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TAX ;SAVE CURRENT IMAGE OF DATA BYTE
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LDA #$00 ;ZERO OUT ACCUMULATOR FOR ADD
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ADC #>AN0OFF ;ADD CARRY TO ANNUNCIATOR ADDRESS
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STA BIT0+1 ;MODIFY THE XMITBITS SUBROUTINE
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TXA ;RESTORE ACCUMULATOR
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;
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JSR XMITBITS ;SEND THE BYTE OUT
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LDX TEMPX
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LDA TEMPA ;RESTORE X AND A
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RTS
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;-----------------------------------------------------------------------
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XMITBITS BIT AN0OFF ;4 CYCLES - TRANSMIT START BIT - ALWAYS LOW
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JSR DELAY22 ;6+22
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BIT0 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT1 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT2 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT3 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT4 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT5 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT6 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT7 BIT AN0OFF ;4
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JSR DELAY22 ;6+22
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BIT AN0ON ;4 ;TRANSMIT STOP BIT - ALWAYS HIGH
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JSR DELAY22 ;6+22
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RTS
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;-----------------------------------------------------------------------
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DELAY22 NOP ;WAIT 22 CYCLES
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NOP
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NOP
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NOP
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NOP
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NOP
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NOP
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NOP
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RTS
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;----------------
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; END OF PROGRAM
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;----------------
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;==================================================
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EOF BRK
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