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https://github.com/sehugg/8bitworkshop.git
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108 lines
1.9 KiB
ArmAsm
108 lines
1.9 KiB
ArmAsm
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TEST = 1
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.module biosasm
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.globl _STIMER,_CTIMER,_BIGFONT,_SMLFONT
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BIOSStart:
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di ; disable interrupts
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ld HL,#0x2000
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.if TEST
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ld HL,#(_main)
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.endif
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ld A,(HL) ; A <- mem[0x2000]
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cp #0x55 ; found sentinel byte? ($55)
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jp Z,FoundSentinel ; yes, load program
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.if TEST
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jp _main ; jump to test program
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.else
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jp 0x2000 ; jump to $2000
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.endif
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FoundSentinel:
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ld SP,#0x4fce ; position stack below BIOS vars
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call _bios_init ; misc. bios init routines
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.if TEST
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ld HL,#(_main+5)
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.else
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ld HL,#0x2005 ; cartridge start vector
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.endif
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ld A,(HL)
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inc HL
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ld H,(HL)
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ld L,A
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jp (HL) ; jump to cart start vector
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.ds 0x38 - (. - BIOSStart) ; eat up space until 0x38
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.globl SYSCALL38
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SYSCALL38:
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push hl
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push af
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push bc
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push de
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push ix
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push iy
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ld hl,#0
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add hl,sp
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push hl ; HL points to context block
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call _SYSCALL ; syscall handler
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pop hl
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pop iy
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pop ix
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pop de
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pop bc
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pop af
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pop hl
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ret
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; out to port
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.globl _portOut
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_portOut:
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ld c,h
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out (c),l
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ret
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.globl _bcdadd8
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_bcdadd8:
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push ix
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ld ix,#0
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add ix,sp
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ld a,6(ix) ; carry
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rrc a ; set carry bit
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ld h,#0 ; carry goes here
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ld a,4(ix) ; a -> A
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adc a,5(ix) ; a + b -> A
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daa ; BCD conversion
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ld l,a ; result -> L
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rl h ; carry -> H
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pop ix
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ret
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;void set_palette(byte palette[8]) __z88dk_fastcall;
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.globl _set_palette
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_set_palette:
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ld bc,#0x80b ; B -> 8, C -> 0xb
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otir ; write C bytes from HL to port[B]
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ret
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.globl _KCTASC_TABLE
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_KCTASC_TABLE:
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.db 0x00
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.db 0x43, 0x5e, 0x5c, 0x25, 0x52, 0x53, 0x3b, 0x2f
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.db 0x37, 0x38, 0x39, 0x2a, 0x34, 0x35, 0x36, 0x2d
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.db 0x31, 0x32, 0x33, 0x2b, 0x26, 0x30, 0x2e, 0x3d
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.ds 0x200 - (. - BIOSStart) ; eat up space until 0x200
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DOPEVector:
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JP _STIMER
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JP _CTIMER
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.db 0x20, 8, 8, 1, 7 ; Font descriptor (big font)
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.dw _BIGFONT
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.db 0xa0, 4, 6, 1, 5 ; Font descriptor (small font)
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.dw _SMLFONT
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.db 0x3f ; all keys mask
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.db 0x3f
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.db 0x3f
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.db 0x3f
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