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Applecorn
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Finished off noise channel for Mockingboard.

This commit is contained in:
Bobbi Webber-Manners 2022-11-28 19:59:19 -05:00
parent 869b0d669c
commit f67069421c
3 changed files with 25 additions and 6 deletions
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BIN
applecorn.po
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2
auxmem.init.s
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@ -290,7 +290,7 @@ BYTE00 BEQ BYTE00A ; OSBYTE 0,0 - generate error
RTS ; %000x1xxx host type, 'A'pple RTS ; %000x1xxx host type, 'A'pple
BYTE00A BRK BYTE00A BRK
DB $F7 DB $F7
HELLO ASC 'Applecorn MOS 2022-11-27' HELLO ASC 'Applecorn MOS 2022-11-28'
DB $00 ; Unify MOS messages DB $00 ; Unify MOS messages
* TO DO: Move into RAM * TO DO: Move into RAM
GSSPEED DB $00 ; $80 if GS is fast, $00 for slow GSSPEED DB $00 ; $80 if GS is fast, $00 for slow

29
mainmem.mock.s
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@ -2,8 +2,8 @@
* (c) Bobbi 2022 GPLv3 * (c) Bobbi 2022 GPLv3
* *
* Mockingboard Driver. * Mockingboard Driver.
* Simulates Hitachi SN76489 sound generator chip found in BBC Micro.
* *
* *
* I borrowed some ideas from Deater: * I borrowed some ideas from Deater:
* https://github.com/deater/dos33fsprogs/blob/master/music/pt3_lib/pt3_lib_mockingboard_setup.s * https://github.com/deater/dos33fsprogs/blob/master/music/pt3_lib/pt3_lib_mockingboard_setup.s
@ -124,9 +124,14 @@ MOCKNOTE PHA
* On entry: X - oscillator number 0-3, Y - frequency to set * On entry: X - oscillator number 0-3, Y - frequency to set
* Preserves X & Y * Preserves X & Y
MOCKFREQ PHX MOCKFREQ PHX
CPX #$00 ; Noise channel CPX #$00 ; Oscillator 0 is noise channel
BEQ :NOISE BEQ :NOISE
TXA CPX #$01 ; Oscillator 1 controls noise freq
BNE :S0 ; Not 1? Skip
CMP #$00 ; If frequency is zero ..
BEQ :S0 ; .. skip
STA :CH1NOTE ; Store frequency for noise gen
:S0 TXA
DEC A ; Subtract 1 DEC A ; Subtract 1
ASL ; Double to get fine register ASL ; Double to get fine register
TAX TAX
@ -137,11 +142,25 @@ MOCKFREQ PHX
JSR MOCKWRT1 ; Write value to AY-3 register JSR MOCKWRT1 ; Write value to AY-3 register
PLX PLX
RTS RTS
:NOISE LDX #6 ; Noise period register :NOISE TYA ; Parameter P
TYA ; TODO TEMPORARY HACK AND #$03 ; Keep least significant 2 bits
TAY
LDA :NOISENOTE,Y ; Get value of note
EOR #$FF ; Negate
INC A
CLC ; Add 255
ADC #$FF
LSR ; Convert 0..255 to 0..31
LSR
LSR
LDX #6 ; Noise period register
JSR MOCKWRT2 ; Write value to AY-3 register JSR MOCKWRT2 ; Write value to AY-3 register
PLX PLX
RTS RTS
:NOISENOTE DB $FF ; BBC Micro note P=0 or 4
DB $80 ; BBC Micro note P=1 or 5
DB $00 ; BBC Micro note P=2 or 6
:CH1NOTE DB $00 ; Note on channel 1
* Adjust amplitude of note already playing * Adjust amplitude of note already playing