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@ -4,8 +4,12 @@ |
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; |
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;====================================================================== |
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; |
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; @3.579545 OCTAVE RANGE IS 2 - 7 (Bb2/A#2 .. A7) |
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; @4.000000 OCTAVE RANGE IS 2 - 7 (B2 .. A7) |
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; AY-3-8910 & YM2149 PSG CHIPS NEED AN INPUT CLOCK FREQUENCY OF |
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; NO MORE THAN 2 MHZ. THE CLOSEST THING THERE IS TO A STANDARD |
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; IS THE MSX FREQ OF 1.7897725 MHZ. |
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; |
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; @1.7897725 OCTAVE RANGE IS 2 - 7 (Bb2/A#2 .. A7) |
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; @2.0000000 OCTAVE RANGE IS 2 - 7 (B2 .. A7) |
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; |
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AY_RCSND .EQU 0 ; 0 = EB MODULE, 1=MF MODULE |
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; |
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@ -14,7 +18,6 @@ AY_RSEL .EQU $9A |
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AY_RDAT .EQU $9B |
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AY_RIN .EQU AY_RSEL |
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AY_ACR .EQU $9C |
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AY_CLK .SET 3579545 ; MSX NTSC COLOUR BURST FREQ = 315/88 |
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#ENDIF |
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; |
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#IF (AYMODE == AYMODE_N8) |
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@ -53,7 +56,6 @@ AY_RSEL .EQU $A0 |
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AY_RDAT .EQU $A1 |
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AY_RIN .EQU AY_RSEL |
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AY_ACR .EQU $A2 |
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AY_CLK .SET 3579545 ; MSX NTSC COLOUR BURST FREQ = 315/88 |
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#ENDIF |
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; |
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;====================================================================== |
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@ -92,14 +94,16 @@ AY_IDAT .EQU 0 ; NO INSTANCE DATA ASSOCIATED WITH THIS DEVICE |
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; |
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AY_TONECNT .EQU 3 ; COUNT NUMBER OF TONE CHANNELS |
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AY_NOISECNT .EQU 1 ; COUNT NUMBER OF NOISE CHANNELS |
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;; |
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;#IF (AY_CLK > 3579545) ; DEPENDING ON THE |
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;AY_SCALE .EQU 2 ; INPUT CLOCK FREQUENCY |
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;#ELSE ; PRESCALE THE TONE PERIOD |
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;AY_SCALE .EQU 3 ; DATA TO MAINTAIN MAXIMUM |
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;#ENDIF ; RANGE AND ACCURACY |
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; |
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#IF (AY_CLK > 3579545) ; DEPENDING ON THE |
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AY_SCALE .EQU 2 ; INPUT CLOCK FREQUENCY |
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#ELSE ; PRESCALE THE TONE PERIOD |
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AY_SCALE .EQU 3 ; DATA TO MAINTAIN MAXIMUM |
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#ENDIF ; RANGE AND ACCURACY |
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; |
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AY_RATIO .EQU (AY_CLK * 100) / (16 >> AY_SCALE) |
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.ECHO "SN76489 CLOCK: " |
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.ECHO SN7CLK |
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.ECHO "\n" |
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; |
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#INCLUDE "audio.inc" |
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; |
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@ -306,38 +310,8 @@ AY_VOLUME: |
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;====================================================================== |
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; |
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AY_NOTE: |
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AUDTRACE(AYT_NOTE) |
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AUDTRACE_HL |
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AUDTRACE_CR |
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; |
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; CALL PRTHEXWORDHL |
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; CALL PC_COLON |
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; |
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LD DE, AY3NOTETBL ; ON ENTRY HL IS THE NOTE TO PLAY |
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PUSH DE ; AND DE IS THE START OF NOTE TABLE |
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LD DE, 48 ; LOAD DE WITH NOTE TABLE SIZE |
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CALL DIV16 ; AND CALCULATE OCTAVE COUNT IN BC |
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; |
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ADD HL, HL ; HL IS THE REMAINDER FROM ABOVE DIVISION (0-47) AND THE NOTE |
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POP DE ; TO PLAY IN THE OCTAVE. ADD IT TO THE START OF THE NOTE TABLE |
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ADD HL, DE ; TO POINT TO THE PERIOD FOR THE NOTE WE WANT TO PLAY. |
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; |
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LD A, (HL) ; HL POINT TO CURRENT PERIOD COUNT WE WANT TO PLAY |
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INC HL ; SO LOAD PERIOD COUNT FROM NOTE TABLE INTO HL |
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LD H, (HL) ; SO WE CAN UPDATE IT FOR THE REQUIRED OCTAVE |
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LD L, A |
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; |
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;LD A,AY_SCALE - 1 ; THE NOTE TABLE PERIOD DATA HAS BEEN |
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LD A,AY_SCALE ; THE NOTE TABLE PERIOD DATA HAS BEEN |
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ADD A,C ; PRESCALED TO MAINTAIN RANGE SO ALLOW |
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LD B,A ; FOR THIS WHEN CHANGING OCTAVE |
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AY_NOTE1: |
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SRL H ; ADJUST THE PERIOD DATA |
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RR L ; FOR THE DESIRED OCTAVE |
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DJNZ AY_NOTE1 ; FALL THROUGH TO SET PERIOD AND RANGE CHECK |
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; |
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; CALL PRTHEXWORDHL |
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; CALL NEWLINE |
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LD DE, AY3NOTETBL |
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CALL AUD_NOTE ; RETURNS PERIOD IN HL, FALL THRU |
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; |
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;====================================================================== |
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; SOUND DRIVER FUNCTION - PERIOD |
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@ -347,21 +321,22 @@ AY_PERIOD: |
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AUDTRACE(AYT_PERIOD) |
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AUDTRACE_HL |
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AUDTRACE_CR |
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LD A, H ; IF ZERO - ERROR |
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; |
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LD A,H ; IF ZERO - ERROR |
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OR L |
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JR Z, AY_PERIOD1 |
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JR Z,AY_PERIOD1 |
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; |
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LD A, H ; MAXIMUM TONE PERIOD IS 12-BITS |
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LD A,H ; MAXIMUM TONE PERIOD IS 12-BITS |
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AND 11110000B ; ALLOWED RANGE IS 0001-0FFF (4095) |
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JR NZ, AY_PERIOD1 ; RETURN NZ IF NUMBER TOO LARGE |
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LD (AY_PENDING_PERIOD), HL ; SAVE AND RETURN SUCCESSFUL |
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JR NZ,AY_PERIOD1 ; RETURN NZ IF NUMBER TOO LARGE |
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LD (AY_PENDING_PERIOD),HL ; SAVE AND RETURN SUCCESSFUL |
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XOR A ; SET SUCCESS |
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RET |
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; |
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AY_PERIOD1: |
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LD A, $FF ; REQUESTED PERIOD IS LARGER |
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LD (AY_PENDING_PERIOD), A ; THAN THE DEVICE CAN SUPPORT |
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LD (AY_PENDING_PERIOD+1), A; SO SET PERIOD TO FFFF |
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LD HL,$FFFF ; REQUESTED PERIOD IS LARGER |
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LD (AY_PENDING_PERIOD),HL ; THAN PSG CAN SUPPORT, SO |
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OR $FF ; SET PERIOD TO $FFFF |
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RET ; AND RETURN FAILURE |
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; |
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;====================================================================== |
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@ -612,10 +587,32 @@ AYT_REGWR .DB "\r\nOUT AY-3-8910 $" |
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; QUARTER TONE FREQUENCY TABLE |
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;====================================================================== |
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; |
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; THE FREQUENCY BY QUARTER TONE STARTING AT A0# OCTAVE 0 |
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; USED TO MAP EACH OCTAVE (DIV BY 2 TO JUMP AN OCTAVE UP) |
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; FIRST PLAYABLE NOTE WILL BE 0 |
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; ASSUMING A CLOCK OF 1843200 THIS MAPS TO A0# |
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; THE FOLLOWING TABLE MAPS A FULL OCTAVE OF QUARTER-NOTES |
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; STARTING AT A# IN OCTAVE 0 TO THE CORRESPONDING PERIOD |
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; VALUE TO USE ON THE PSG TO ACHIEVE THE DESIRED NOTE FREQUENCY. |
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; |
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; THE FREQUENCY PRODUCED BY THE AY-3-8910 IS: |
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; FREQ = CLOCK / 16 / PERIOD |
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; |
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; SO, TO MAP A DESIRED FREQUENCY TO A PERIOD, WE USE: |
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; PERIOD = CLOCK / 16 / FREQ |
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; |
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; IN ORDER TO IMPROVE THE RESOLUTION OF THE FREQUENCY |
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; VALUE USED, WE ALSO MULTPLY BOTH SIDES OF THE EQUATION |
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; BY 100: |
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; PERIOD * 100 = (CLOCK / 16 / FREQ) * 100 |
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; |
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; THE RESULTING PERIOD VALUE CAN BE REPEATEDLY HALVED |
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; TO TO JUMP UP AS MANY OCTAVES AS DESIRED. |
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; |
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; THE FINAL VALUE IS SHIFTED BY AUD_SCALE BITS |
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; IN ORDER TO IMPROVE THE RESOLUTION. THIS FINAL SHIFT |
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; IS REMOVED WHEN IN THE AY_NOTE ROUTINE. |
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; |
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; ASSUMING A CLOCK OF 1.7897725 MHZ, THE FIRST PLAYABLE |
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; NOTE WILL BE A0#/B0b (HBIOS NOTE CODE 0). |
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; |
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AY_RATIO .EQU (AY_CLK * 100) / (16 >> AUD_SCALE) |
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; |
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AY3NOTETBL: |
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.DW AY_RATIO / 2913 ; A0#/B0b 178977250 / 2913 = 61440; PROOF: 61440 >> 3 = 7680, 3579545 / 7680 / 16 = 29.13 |
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Wayne Warthen
3 years ago