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.
65 lines
1.0 KiB
ArmAsm
65 lines
1.0 KiB
ArmAsm
; CPU speed manipulation.
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; Switches to normal speed. No effect on DMG.
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; Preserved: BC, DE, HL
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cpu_norm:
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; Do nothing if not CGB
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ld a,(gb_id)
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and gb_id_cgb
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ret z
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lda KEY1
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rlca
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ret nc
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jr cpu_speed_toggle
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; Switches to double speed. No effect on DMG.
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; Preserved: BC, DE, HL
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cpu_fast:
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; Do nothing if not CGB
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ld a,(gb_id)
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and gb_id_cgb
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ret z
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lda KEY1
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rlca
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ret c
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cpu_speed_toggle:
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di
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lda IE
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push af
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xor a
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sta IE
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sta IF
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wreg P1,$30
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wreg KEY1,1
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stop
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nop
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pop af
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sta IE
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ret
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; Determines current CPU speed without using KEY1.
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; A=1 if fast, 0 if normal. Always 0 on DMG.
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; Preserved: BC, DE,HL
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get_cpu_speed:
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push bc
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call sync_apu
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wreg NR14,$C0
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wreg NR11,-1
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wreg NR12,8
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wreg NR14,$C0
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ld bc,-$262
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- inc bc
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lda NR52
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and 1
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jr nz,-
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ld a,0
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bit 7,b
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jr nz,+
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inc a
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+ pop bc
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ret
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