238 lines
3.1 KiB
Z80 Assembly
238 lines
3.1 KiB
Z80 Assembly
.global set_frame
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.global get_free_frame
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.global pmem_init
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RAM_TYPE equ 2
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SHARED_DATA_PAGE equ 2
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BMAP_PAGE_512K equ 3
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RAM_SIZE_LOW_PORT equ 0xFD
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RAM_SIZE_HIGH_PORT equ 0xFE
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BANKING_PAGE equ 0xE
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ram_nums equ BANKING_PAGE << 12
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first_ram_card: .db 0
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; Get the pointer to the specified RAM card's bitmap.
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; Also maps the right frame in
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; A contains the RAM card to use
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; HL returns the pointer to the bitmap
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; The values in A, BC, DE, and IX are destroyed.
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get_ram_bmap:
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ex af, af'
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ld a, (first_ram_card)
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ld b, a
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ld c, BANKING_PAGE
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ld d, 0
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ld e, SHARED_DATA_PAGE
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call set_frame
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ex af, af'
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ld b, a
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ld c, 0xFD
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in l, (c)
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inc c
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in h, (c)
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ex af, af'
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ld a, h
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cp 0
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jp nz, grb_large_card
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ld a, l
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cp 128
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jp nz, grb_large_card
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; grb_512k_card
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ld l, a
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ld a, (first_ram_card)
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ld b, a
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ld c, BANKING_PAGE
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ld d, 0
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ld e, BMAP_PAGE_512K
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call set_frame
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ex af, af'
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ld h, 0
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ld l, a
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add hl, hl
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add hl, hl
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add hl, hl
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add hl, hl
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ld a, h
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or 0xE0
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ld h, a
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grb_512k_done:
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ret
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grb_large_card:
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ex af, af'
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ld b, a
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ld c, 0xF
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ld d, 0
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ld e, d
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call set_frame
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ld hl, 0xE000
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grb_large_done:
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ret
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; Get a free frame of RAM
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; On return, C contains the card that the frame is in, and
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; HL contains the frame number
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; The values in A, B, D, E, IX, and IY are destroyed.
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get_free_frame:
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push bc
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ld a, (first_ram_card)
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ld b, a
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ld c, BANKING_PAGE
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ld d, 0
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ld e, SHARED_DATA_PAGE
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call set_frame
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pop bc
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gff_loop:
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ld ix, ram_nums
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ld a, (ix+0)
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cp 0
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jp z, gff_done
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push af
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push ix
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call get_ram_bmap
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pop ix
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push hl
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pop iy
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pop af
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push iy
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ld b, a
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ld c, 0xFD
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in l, (c)
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inc c
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in h, (c)
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srl h
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rr l
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srl h
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rr l
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srl h
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rr l
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ld b, h
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ld c, l
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byte_loop:
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push bc
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ld b, 8
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ld c, a
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bit_loop:
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ld a, b
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sub 1
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sla a
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sla a
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sla a
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or 0x47
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ld (bit_ins+1), a
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or 0x80
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ld (gff_set_ins+1), a
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ld a, (iy+0)
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bit_ins: bit 0, a
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jp nz, used_frame
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pop de
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pop de
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push iy
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pop hl
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ld a, (hl)
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gff_set_ins: set 0, a
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ld (hl), a
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scf
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ccf
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sbc hl, de
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add hl, hl
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add hl, hl
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add hl, hl
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ld a, b
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sub 1
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add a, l
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ld l, a
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ret
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used_frame:
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djnz bit_loop
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ld d, c
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pop bc
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dec bc
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inc iy
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ld a,b
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or c
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ld a, d
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jp nz,byte_loop
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inc ix
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pop iy
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jp gff_loop
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gff_done:
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exx
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ld c, 0
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ld hl, 0
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ret
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pmem_init:
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ld b, RAM_TYPE
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call find_first_card
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ld a, l
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ld (first_ram_card), a
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ex af, af'
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ld c, BANKING_PAGE
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ld b, l
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ld d, 0
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ld e, SHARED_DATA_PAGE
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call set_frame
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ld ix, ram_nums
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ld b, 16
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ld c, RAM_TYPE
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call get_all_cards
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ld ix, ram_nums
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init_loop:
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ld a, (ix+0)
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inc ix
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cp 0
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jp z, init_done
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ld b, a
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ld c, RAM_SIZE_LOW_PORT
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in l, (c)
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ld c, RAM_SIZE_HIGH_PORT
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in h, (c)
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push hl
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pop iy
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ld d, a
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push af
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ld a, d
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call get_ram_bmap
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pmem_init_grb_done:
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pop af
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push hl
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push iy
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pop bc
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ld d, h
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ld e, l
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ld (hl), 0 ; Zero out the first byte ( Acts as a 'seed' for the zeroing )
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ldir
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pop hl
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ld b, a
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push iy
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pop de
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ld a, d
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cp 0
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jp nz, init_if1
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ld a, e
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cp 128
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jp nz, init_if1
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jp init_if1_end
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init_if1:
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ld (hl), 0x1
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init_if1_end:
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/* ld a, (first_ram_card) */
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/* ld c, a */
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/* ld a, b */
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/* cp c */
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jp nz, init_if2_end
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ld (hl), 0xFF
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inc hl
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ld (hl), 0xFF
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init_if2_end:
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ld a, (first_ram_card)
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ld b, a
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ld c, BANKING_PAGE
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ld d, 0
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ld e, SHARED_DATA_PAGE
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call set_frame
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jp init_loop
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init_done:
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ret
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