Initial upload, Echo 0.8 UNSTABLE VERSION

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