Ajurna
918c9020b5
Introduced symbol files for various Game Boy systems (CGB, AGB, MGB, SGB) to define boot sequences and functionalities. Included CPU instruction behavior tests, with detailed coverage of standard operations and interrupt handling. Added documentation for test execution and internal framework operations.
89 lines
1.5 KiB
ArmAsm
89 lines
1.5 KiB
ArmAsm
; Fast table-based CRC-32
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.define crc_tables (bss+$FF)&$FF00 ; 256-byte aligned
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.redefine bss crc_tables+$400
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; Initializes fast CRC tables and resets checksum.
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; Time: 47 msec
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init_crc_fast:
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ld l,0
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@next:
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xor a
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ld c,a
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ld d,a
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ld e,l
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ld h,8
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- rra
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rr c
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rr d
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rr e
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jr nc,+
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xor $ED
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ld b,a
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ld a,c
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xor $B8
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ld c,a
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ld a,d
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xor $83
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ld d,a
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ld a,e
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xor $20
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ld e,a
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ld a,b
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+ dec h
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jr nz,-
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ld h,>crc_tables
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ld (hl),e
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inc h
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ld (hl),d
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inc h
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ld (hl),c
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inc h
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ld (hl),a
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inc l
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jr nz,@next
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jp init_crc
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; Faster version of update_crc
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; Preserved: BC, DE
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; Time: 50 cycles (including CALL)
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update_crc_fast:
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; Fastest inline macro version of update_crc_fast
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; Time: 40 cycles
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; Size: 28 bytes
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.macro update_crc_fast
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ld l,a ; 1
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lda checksum ; 3
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xor l ; 1
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ld l,a ; 1
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ld h,>crc_tables ; 2
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lda checksum+1 ; 3
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xor (hl) ; 2
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inc h ; 1
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sta checksum ; 3
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lda checksum+2 ; 3
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xor (hl) ; 2
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inc h ; 1
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sta checksum+1 ; 3
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lda checksum+3 ; 3
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xor (hl) ; 2
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inc h ; 1
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sta checksum+2 ; 3
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ld a,(hl) ; 2
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sta checksum+3 ; 3
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.endm
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update_crc_fast
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ret
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