aboutsummaryrefslogtreecommitdiff
path: root/src-z80/core/main.z80
diff options
context:
space:
mode:
Diffstat (limited to 'src-z80/core/main.z80')
-rw-r--r--src-z80/core/main.z80330
1 files changed, 330 insertions, 0 deletions
diff --git a/src-z80/core/main.z80 b/src-z80/core/main.z80
new file mode 100644
index 0000000..4018a1b
--- /dev/null
+++ b/src-z80/core/main.z80
@@ -0,0 +1,330 @@
+;****************************************************************************
+; EntryPoint
+; Where the program starts
+;****************************************************************************
+
+EntryPoint:
+ ld sp, RAM_Stack ; Init stack
+
+ xor a ; Reset Echo status
+ ld (RAM_Status), a
+
+ ld hl, $7F11 ; Mute PSG
+ ld (hl), $9F
+ ld (hl), $BF
+ ld (hl), $DF
+ ld (hl), $FF
+ xor a
+ ld (RAM_PSGData), a
+ ld (RAM_PSGData+16), a
+ ld (RAM_PSGData+32), a
+ ld (RAM_PSGData+48), a
+
+ ld hl, $6000 ; Set default bank
+ ld (hl), l
+ ld (hl), l
+ ld (hl), l
+ ld (hl), l
+ ld (hl), l
+ ld (hl), l
+ ld (hl), l
+ ld (hl), l
+ ld (hl), l
+
+ ;ex af, af' ; Set 9th bank bit to 0 by default
+ ;xor a ; (0 = $000000-$7FFFFF range aka MD mode)
+ ;ex af, af' ; (1 = $800000-$FFFFFF range aka 32X mode)
+
+ ld ix, $4000 ; YM2612 I/O ports base address
+ ld iyh, $40
+
+ exx ; Init PCM playback status
+ ld bc, $0000 ; B = playing, C = bank
+ ld de, $0000 ; DE = address
+ ld hl, $6000 ; HL = always $6000
+ exx
+
+ ld (ix+0), $2B ; Disable DAC by default
+ ld (ix+1), $00
+
+ ld e, $7F ; Mute all FM channels
+ ld a, $40
+ ld b, 4
+.mutefm:
+ ld (ix+0), a
+ ld (ix+1), e
+ ld (ix+2), a
+ ld (ix+3), e
+ inc a
+ ld (ix+0), a
+ ld (ix+1), e
+ ld (ix+2), a
+ ld (ix+3), e
+ inc a
+ ld (ix+0), a
+ ld (ix+1), e
+ ld (ix+2), a
+ ld (ix+3), e
+ inc a
+ inc a
+ djnz .mutefm
+
+ ld (ix+0), $B4 ; Ensure all channels can be heard from both
+ ld (ix+1), $C0 ; speakers (by default they're mute!)
+ ld (ix+0), $B5
+ ld (ix+1), $C0
+ ld (ix+0), $B6
+ ld (ix+1), $C0
+ ld (ix+2), $B4
+ ld (ix+3), $C0
+ ld (ix+2), $B5
+ ld (ix+3), $C0
+ ld (ix+2), $B6
+ ld (ix+3), $C0
+
+ ld (ix+0), $24 ; Init timers
+ ld (ix+1), $FE
+ ld (ix+0), $25
+ ld (ix+1), $03
+ ld (ix+0), $26
+ ld (ix+0), $C9
+ ld (ix+1), $FF
+ ld (ix+0), $27
+ ld (ix+1), $3F
+
+ jp IdleLoop ; Go into idle loop
+
+;****************************************************************************
+; PollPCM
+; Used to update PCM while not idle
+;****************************************************************************
+
+PollPCM: macro
+ ld a, ($4000)
+ bit 0, a
+ call nz, UpdatePCM
+ endm
+
+;****************************************************************************
+; RunCommand
+; Checks which command to run
+;****************************************************************************
+
+RunCommand:
+ dec a ; Command $01: load list
+ jp z, LoadList
+ dec a ; Command $02: play SFX
+ jp z, PlaySFX
+ dec a ; Command $03: stop SFX
+ jp z, StopSFXCmd
+ dec a ; Command $04: play BGM
+ jp z, PlayBGM
+ dec a ; Command $05: stop BGM
+ jp z, StopBGMCmd
+
+ PollPCM
+
+ xor a ; Bad command, ignore >:(
+ ld (RAM_Command), a
+
+ PollPCM
+
+;****************************************************************************
+; IdleLoop
+; Loop that runs when not processing SFX or BGM
+;****************************************************************************
+
+IdleLoop:
+ ld a, (RAM_Command) ; Look for commands
+ or a
+ jr nz, RunCommand
+
+ PollPCM ; Poll PCM
+
+ ld a, ($4000) ; Tick?
+ bit 1, a
+ jr nz, DoTick
+ bit 0, a ; Poll PCM again
+ call nz, UpdatePCM ; Not using macro for optimization purposes
+
+ jp IdleLoop ; Keep idling
+
+;****************************************************************************
+; DoTick
+; Called whenever a new tick triggers
+;****************************************************************************
+
+DoTick:
+ ld a, (ix+0)
+ bit 0, a
+ call nz, UpdatePCM
+
+ ld (ix+0), $26 ; Reset timer
+.timerset:
+ ld (ix+1), $C8
+ ld (ix+0), $27
+ ld (ix+1), $2F
+
+ ld a, (.timerset+3) ; $C8 is too fast, $C9 is too slow
+ xor $01 ; So, we alternate between them to compensate
+ ld (.timerset+3), a
+
+ PollPCM
+
+DoTick_SFX: ; Process SFXs
+ jp DoTick_SFXSkip
+DoTick_SFXSkip:
+
+ PollPCM
+
+DoTick_BGM: ; Process BGMs
+ jp DoTick_BGMSkip
+DoTick_BGMSkip:
+
+ PollPCM
+
+ jp UpdatePSG ; Update PSG envelopes
+DoTick_PSGSkip:
+
+ PollPCM
+
+ jp IdleLoop ; End of subroutine
+
+;****************************************************************************
+; BankSwitch
+; Switches into a new bank (won't update player status!)
+;
+; input A .... New bank to switch into
+; input HL ... Must be $6000
+; breaks ..... AF
+;****************************************************************************
+
+BankSwitch: macro
+ ld (hl), a
+ rrca
+ ld (hl), a
+ rrca
+ ld (hl), a
+ rrca
+ ld (hl), a
+ rrca
+ ld (hl), a
+ rrca
+ ld (hl), a
+ rrca
+ ld (hl), a
+ ld (hl), l
+ rrca
+ ld (hl), a
+ endm
+
+;****************************************************************************
+; LoadList [command $01]
+; Loads the pointer list
+;****************************************************************************
+
+LoadList:
+ ld hl, RAM_ComBank ; Get command parameters
+ ld c, (hl)
+ inc l
+ ld e, (hl)
+ inc l
+ ld d, (hl)
+ ex de, hl
+
+ xor a ; Command parsed
+ ld (RAM_Command), a
+
+ ld a, c ; Do initial bank switch
+ ld de, $6000
+ ex de, hl
+ BankSwitch
+ ex de, hl
+
+ ld de, RAM_PointerList ; Where the pointer list starts
+
+.loop:
+ ld a, (hl) ; Get high address byte
+ or a ; Is it the end of the list?
+ jp z, .end ; If so, stop parsing list
+ ld (de), a ; Nope, store it in list
+
+ inc d ; Get address for next byte
+ inc l
+ jr nz, .noswitch1
+ inc h
+ jr nz, .noswitch1
+ inc c
+ ld a, c
+ ld h, $60
+ BankSwitch
+ ld h, $80
+.noswitch1:
+
+ ld a, (hl) ; Get low address byte
+ ld (de), a ; Store it in pointer list
+
+ inc d ; Get address for next byte
+ inc l
+ jr nz, .noswitch2
+ inc h
+ jr nz, .noswitch2
+ inc c
+ ld a, c
+ ld h, $60
+ BankSwitch
+ ld h, $80
+.noswitch2:
+
+ ld a, (hl) ; Get bank byte
+ ld (de), a ; Store it in pointer list
+
+ dec d ; Get address for next byte
+ dec d
+ inc e
+ inc l
+ jr nz, .noswitch3
+ inc h
+ jr nz, .noswitch3
+ inc c
+ ld a, c
+ ld h, $60
+ BankSwitch
+ ld h, $80
+.noswitch3:
+
+ jp .loop ; Go for next byte
+
+.end:
+ ld a, c ; Store current bank
+ ld (RAM_LastBank), a
+ jp IdleLoop ; End of subroutine
+
+;****************************************************************************
+; GetParam
+; Subroutine for getting the parameter byte
+;****************************************************************************
+
+GetParam:
+ ld a, (RAM_LastBank) ; Bank switch?
+ cp c
+ jp z, .noswitchp
+ ld a, c
+ ld (RAM_LastBank), a
+ exx
+ BankSwitch
+ exx
+.noswitchp:
+ ld b, (hl) ; Get volume
+
+ PollPCM
+
+ inc l ; Get next address
+ jp nz, .nonewbankp
+ inc h
+ jp nz, .nonewbankp
+ ld h, $80
+ inc c
+.nonewbankp:
+
+ ret ; End of subroutine