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56 lines
1.0 KiB
56 lines
1.0 KiB
SECTION "Utilities", ROM0
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; Busy-wait until vertical blank occurs
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wait_for_vblank::
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ld a, [$ff41]
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and 3
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cp 1
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jr nz, wait_for_vblank
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ret
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; Copy data between two regions (takes 40*N+12 cycles)
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; @param bc Pointer to the destination region
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; @param hl Pointer to the source region
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; @param d Size (in bytes) to copy. Must be >0
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; @destroy a, b, c, d, h, l
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memcpy::
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ld a, [hli] ; 8
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ld [bc], a ; 8
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inc bc ; 8
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dec d ; 4
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jr nz, memcpy ; 12/8
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ret ; 16
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; Fill a memory region with a value
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; @param hl Pointer to the destination region
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; @param a Byte to fill with
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; @param c Number of bytes to fill. Must be >0
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; @destroy a, c, hl
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memset::
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ld [hli], a
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dec c
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jr nz, memset
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ret
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; Divide a value by 10 (http://homepage.divms.uiowa.edu/~jones/bcd/decimal.html#division)
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; @param b Dividend
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; @return a Quotient
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; @destroy b
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div10::
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ld a, b
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srl a
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srl a
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add b
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srl a
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add b
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srl a
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srl a
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srl a
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add b
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srl a
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add b
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srl a
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srl a
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srl a
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srl a
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ret
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