158 lines
4.6 KiB
Plaintext
158 lines
4.6 KiB
Plaintext
; TEMPOCHG.SRC
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;
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; THIS SUBROUTINE IS USED TO CALCULATE THE SPEED VALUE TO BE USED WHEN
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; A TEMPO CHANGE META EVENT IS FOUND.
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; INPUT:
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; RESOLUTION (2 BYTES) = LAST 2 BYTES OF MIDI FILE HEADER
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; NEWTEMPO (3 BYTES) = VALUES FROM THE FF 51 03 META EVENT
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; OUTPUT:
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; NEWSPEED (1 BYTE) = NEW SPEED VALUE. YOUR PROGRAM MAY WANT TO
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; ADJUST THIS BASED ON USER'S PREFERENCES.
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;
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TEMPOCHG JSR TMPOSTRT
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JMP LOOKUP
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DIVISION JMP DIVIDE
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;
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; PUBLIC VARIABLES
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RESHI DFB $00
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RESLO DFB $00
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TMPOHI DFB $00
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TMPOMED DFB $00
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TMPOLO DFB $00
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NEWSPEED DFB $00
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;
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; PRIVATE VARIABLES
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DIVIDEND DFB $00,$00,$00,$00
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DIVISOR DFB $00,$00
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QUOTIENT DFB $00,$00,$00,$00
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REMAINDR DFB $00,$00
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TEMPDIV DFB $00,$00,$00
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TEMPDSR DFB $00,$00
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;
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TMPOSTRT LDA #$00
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STA DIVIDEND
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LDA TMPOHI
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STA DIVIDEND+1
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LDA TMPOMED
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STA DIVIDEND+2
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LDA TMPOLO
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STA DIVIDEND+3
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LDA RESHI
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STA DIVISOR
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LDA RESLO
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STA DIVISOR+1
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;
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DIVIDE CLD
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LDA #$00
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STA QUOTIENT
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STA QUOTIENT+1
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STA QUOTIENT+2
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STA QUOTIENT+3
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STA REMAINDR
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STA REMAINDR+1
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STA TEMPDIV
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STA TEMPDIV+1
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STA TEMPDIV+2
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LDA DIVISOR
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STA TEMPDSR
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LDA DIVISOR+1
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STA TEMPDSR+1
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LDA TEMPDSR
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BNE NODIV0
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LDA TEMPDSR+1
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BNE NODIV0
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BRK
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;
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NODIV0 LDY #32 ;DIVIDEND WILL BE SHIFTED 32 TIMES
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DIVLOOP ASL DIVIDEND+3
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ROL DIVIDEND+2
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ROL DIVIDEND+1
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ROL DIVIDEND ;MOVE 1 BIT TO TEMPORARY DIVIDEND
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ROL TEMPDIV+2
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ROL TEMPDIV+1
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ROL TEMPDIV ;NOW CHECK IF TEMPDSR < TEMPDIV
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LDA TEMPDIV
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BNE NOTLESS
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LDA TEMPDIV+1
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CMP TEMPDSR
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BCC LESS
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BNE NOTLESS
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LDA TEMPDIV+2
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CMP TEMPDSR+1
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BCS NOTLESS
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LESS CLC ;STORE A 0 IN THE QUOTIENT
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ROL QUOTIENT+3
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ROL QUOTIENT+2
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ROL QUOTIENT+1
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ROL QUOTIENT
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CLV
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BVC NEXTBIT
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NOTLESS SEC ;SUBTRACT TEMPDSR FROM TEMPDIV
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LDA TEMPDIV+2
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SBC TEMPDSR+1
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STA TEMPDIV+2
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LDA TEMPDIV+1
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SBC TEMPDSR
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STA TEMPDIV+1
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LDA TEMPDIV
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SBC #$00
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STA TEMPDIV
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SEC ;AND STORE A 1 IN THE QUOTIENT
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ROL QUOTIENT+3
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ROL QUOTIENT+2
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ROL QUOTIENT+1
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ROL QUOTIENT
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NEXTBIT DEY
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BNE DIVLOOP ;WHEN DONE, QUOTIENT HAS RESULT, TDIV HAS RMDR
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LDA TEMPDIV+1
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STA REMAINDR
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LDA TEMPDIV+2
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STA REMAINDR+1
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RTS
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;
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LOOKUP LDY #2 ;LOOKUP QUOTIENT IN TEMPO TABLE-STARTING WITH 2
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; ;BECAUSE IF LESS THAN VALUE OF 2 SHOULD USE 1
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LDA QUOTIENT
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BEQ Q3BYT
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QBIG LDY #127
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CLV
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BVC STORSPED
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Q3BYT LDA QUOTIENT+1
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BNE QBIG
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; ;WE HAVE A 2 BYTE QUOTIENT TO LOOK UP
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Q2LOOP LDA QUOTIENT+2
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CMP TEMPOHI,Y
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BCC FOUNDSP
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BNE NEXTSPED
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LDA QUOTIENT+3
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CMP TEMPOLO,Y
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BCC FOUNDSP
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NEXTSPED INY
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CPY #128
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BCC Q2LOOP
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FOUNDSP DEY
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STORSPED STY NEWSPEED
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RTS
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;
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; THE FOLLOWING DATA WAS CREATED BY BASIC PROGRAM "TEMPOCALC"
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; IT REPRESENTS THE EVALUATION OF FUNCTION .4889*(26+27*A+5*A*A) FROM 0-127
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;
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TEMPOHI DFB 0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2
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DFB 3,3,4,4,4,5,5,6,6,7,7,8,8,9,10,10
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DFB 11,12,12,13,14,15,15,16,17,18,19,19,20,21,22,23
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DFB 24,25,26,27,28,29,30,31,32,34,35,36,37,38,39,41
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DFB 42,43,45,46,47,49,50,51,53,54,56,57,59,60,62,63
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DFB 65,66,68,70,71,73,75,76,78,80,82,83,85,87,89,91
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DFB 93,94,96,98,100,102,104,106,108,110,112,114,116,119,121,123
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DFB 125,127,130,132,134,136,139,141,143,146,148,150,153,155,158,160
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TEMPOLO DFB 12,28,48,74,104,139,179,224,18,73,133,197,11,85,164,248
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DFB 81,175,18,121,230,87,206,73,201,78,216,103,250,147,48,211
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DFB 122,38,215,141,71,7,204,149,99,55,15,236,206,180,160,145
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DFB 134,128,127,132,141,154,173,197,225,3,41,84,132,185,243,50
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DFB 118,190,12,94,181,17,114,216,67,179,39,161,31,162,42,183
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DFB 73,224,123,28,193,108,27,207,136,70,9,208,157,110,69,32
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DFB 0,229,207,190,177,170,167,170,177,189,206,228,254,30,67,108
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DFB 154,206,6,67,133,203,23,104,189,23,119,219,68,178,36,156
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;
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CHN MFF0DRVR.SC6
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