299 lines
3.6 KiB
Z80 Assembly
299 lines
3.6 KiB
Z80 Assembly
.global mb_send
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; Sends a message to the MB whose ID is in HL,
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; with the message pointer in C:DE:IX
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; Returns 0 in B if it sent the mesage, of 1 if the box was full
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mb_send:
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push de
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push bc
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push ix
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call get_mb_ptr
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pop ix
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pop bc
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pop de
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push ix
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push hl
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pop ix
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pop hl
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ld ixl, 0xFC
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ld a, (ix+0)
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inc a
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cp 42
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jp nz, no_wrap
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ld a, 0
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no_wrap:
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ld b, (ix+1)
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cp b
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jp nz, mb_not_full
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ld b, 1
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ret
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mb_not_full:
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ld a, (ix+0)
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ld ixl, 0
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ld b, a
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sla a
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sla a
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sla b
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add a, b
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ld ixl, a
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ld (ix+0), c
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ld (ix+1), e
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ld (ix+2), d
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ld (ix+3), l
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ld (ix+4), h
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ld ixl, 0xFC
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ld a, (ix+0)
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inc a
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cp 42
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jp nz, mbs_no_wrap
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ld a, 0
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mbs_no_wrap:
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ld (ix+0), a
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ld b, 0
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ret
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.global mb_read
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;Reads a message from the MB specified in HL,
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; and returns the pointer in C:DE:HL.
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; Returns 0 in B if the mailbox had a message, and 1 if it was full
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mb_read:
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call get_mb_ptr
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mb_read_gmbp_done:
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push hl
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pop ix
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ld ixl, 0xFC
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ld a, (ix+1)
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ld b, (ix+0)
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ld ixl, 0x0
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cp b
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jp nz, mb_not_empty
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ld b, 1
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ret
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mb_not_empty:
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ld b, a
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sla a
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sla a
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sla b
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add a, b
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ld ixl, a
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ld c, (ix+0)
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ld e, (ix+1)
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ld d, (ix+2)
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ld l, (ix+3)
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ld h, (ix+4)
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ld ixl, 0xFC
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ld a, (ix+1)
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inc a
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cp 42
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jp nz, mbr_no_wrap
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ld a, 0
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mbr_no_wrap:
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ld (ix+1), a
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ld b, 0
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ret
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.global get_free_mailbox
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; Gets a free mailbox
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; ID is returned in HL
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get_free_mailbox:
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ld a, (mb_free_list)
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cp 0
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jp nz, gfm_list_not_empty
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ld a, (mb_free_list+1)
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cp 0
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jp nz, gfm_list_not_empty
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gfm_list_empty:
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ld hl, (mb_next_frame_num)
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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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push hl
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ld bc, (mb_next_frame_num)
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inc bc
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ld (mb_next_frame_num), bc
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call get_mb_ptr
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push hl
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pop ix
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pop hl
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push hl
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inc hl
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/* push hl */
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/* pop iy */
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link_loop:
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ld (ix + 0), l
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ld (ix + 1), h
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inc hl
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inc ixh
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ld a, ixh
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cp 0xef
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jp nz, link_loop
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link_loop_done:
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ld (ix + 0), 0
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ld (ix + 1), 0
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pop hl
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ld (mb_free_list), hl
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ld bc, (mb_free_list)
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inc bc
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ld (mb_free_list), bc
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ret
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gfm_list_not_empty:
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ld a, (mb_free_list)
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ld (temp), a
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ld a, (mb_free_list + 1)
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ld (temp + 1), a
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ld hl, (mb_free_list)
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call get_mb_ptr
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push hl
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pop ix
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ld a, (ix + 0)
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ld (mb_free_list), a
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ld a, (ix + 1)
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ld (mb_free_list + 1), a
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ld hl, (temp)
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ret
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; Clobbers A, BC, DE, and IX
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get_mb_ptr:
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ld a, h
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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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srl a
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srl a
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ld b, a
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sla a
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add a, b
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ld ix, mb_frame_list_frames
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ld b, 0
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ld c, a
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add ix, bc
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ld b, (ix + 0)
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ld a, b
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cp 0
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jp z, gmbp_no_frame_list_frame
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ld b, (ix + 0)
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ld e, (ix + 1)
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ld d, (ix + 2)
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ld c, 0xE
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push ix
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call set_frame
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pop ix
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gmbp_has_frame_list_frame:
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push hl
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ld a, h
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and 0x3F
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ld h, a
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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 a, l
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and 0xFC
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ld l, a
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ld a, h
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or 0xE0
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ld h, a
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ld b, (hl)
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ld a, b
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cp 0
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jp z, gmbp_no_frame
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inc hl
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ld e, (hl)
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inc hl
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ld d, (hl)
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ld c, 0xE
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call set_frame
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gmbp_has_frame:
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pop hl
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ld a, l
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and 0xF
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or 0xE0
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ld h, a
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ld l, 0x0
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gmbp_done:
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ret
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gmbp_no_frame_list_frame:
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push hl
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push ix
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call get_free_frame
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pop ix
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push hl
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pop de
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ld (ix + 0), c
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ld (ix + 1), e
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ld (ix + 2), d
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pop hl
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ld b, c
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ld c, 0xE
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push ix
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call set_frame
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pop ix
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push bc
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push de
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push hl
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ld bc, 0x1000
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ld de, 0xE000
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ld h, d
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ld l, e
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ld (hl), 0 ; Zero out the first byte in the segment ( Acts as a 'seed' for the zeroing )
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ldir
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gbmp_no_flf_zeroed:
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pop hl
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pop de
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pop bc
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jp gmbp_has_frame_list_frame
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gmbp_no_frame:
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push hl
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push ix
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call get_free_frame
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pop ix
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push hl
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pop de
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pop hl
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push bc
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push de
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ld b, (ix + 0)
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ld e, (ix + 1)
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ld d, (ix + 2)
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ld c, 0xE
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call set_frame
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pop de
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pop bc
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ld (hl), c
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inc hl
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ld (hl), e
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inc hl
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ld (hl), d
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dec hl
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dec hl
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ld b, c
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ld c, 0xE
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push ix
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call set_frame
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pop ix
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push bc
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push de
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push hl
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ld bc, 0x1000
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ld de, 0xE000
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ld h, d
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ld l, e
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ld (hl), 0 ; Zero out the first byte in the segment ( Acts as a 'seed' for the zeroing )
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ldir
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gbmp_no_f_zeroed:
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pop hl
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pop de
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pop bc
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jp gmbp_has_frame
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temp: .ds.b 5
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mb_free_list: .ds.b 2
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mb_frame_list_frames: .ds.b 3*4
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mb_next_frame_num: .ds.b 2
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