150 lines
2.5 KiB
Z80 Assembly
150 lines
2.5 KiB
Z80 Assembly
.global set_frame
|
|
.global get_frame
|
|
.global clear_frame
|
|
.global vmem_init
|
|
.global vmem_mapping_card
|
|
.global vmem_mapping_bank_low
|
|
.global vmem_mapping_bank_high
|
|
.global pmap_set
|
|
.global pmap_load
|
|
|
|
; map a RAM frame into memory
|
|
; C contains the page to map
|
|
; B contains the card # to use
|
|
; DE contains the bank # in the card
|
|
; The contents of A, IX and C are destroyed
|
|
set_frame:
|
|
ld a, c
|
|
ld (card_set+2), a
|
|
ld (low_set+2), a
|
|
ld (high_set+2), a
|
|
ld ix, vmem_mapping_card
|
|
card_set: ld (ix+0), b
|
|
ld ix, vmem_mapping_bank_low
|
|
low_set: ld (ix+0), e
|
|
ld ix, vmem_mapping_bank_high
|
|
high_set: ld (ix+0), d
|
|
ld a, e
|
|
out (c), a
|
|
ld a, c
|
|
or 0x20
|
|
ld c, a
|
|
ld a, d
|
|
or 0x80
|
|
out (c), a
|
|
ret
|
|
|
|
; Get the RAM frame a page is mapped to
|
|
; C contains the page to get
|
|
; B will contain the card #
|
|
; DE will contain the bank # in the card
|
|
; The contents of A, IX are destroyed
|
|
; If the page is unmapped, C will be 0 and DE will contain garbage
|
|
get_frame:
|
|
ld a, c
|
|
ld (vgf_card_get+2), a
|
|
ld (vgf_low_get+2), a
|
|
ld (vgf_high_get+2), a
|
|
ld ix, vmem_mapping_card
|
|
vgf_card_get: ld b, (ix+0)
|
|
ld ix, vmem_mapping_bank_low
|
|
vgf_low_get: ld e, (ix+0)
|
|
ld ix, vmem_mapping_bank_high
|
|
vgf_high_get: ld d, (ix+0)
|
|
ret
|
|
|
|
; Unmaps a memory page
|
|
; C contains the page to unmap
|
|
; The contents of A, BC, DE, and IX are destroyed
|
|
clear_frame:
|
|
call get_frame
|
|
ld a, c
|
|
ld (vcf_card_set+2), a
|
|
ld ix, vmem_mapping_card
|
|
vcf_card_set: ld (ix+0), 0
|
|
xor a
|
|
out (c), a
|
|
ld a, c
|
|
or 0x20
|
|
ld c, a
|
|
xor a
|
|
out (c), a
|
|
ret
|
|
|
|
; Loads a pagemap pointed to by IX
|
|
; The contents of A, BC, DE, and IX are destroyed
|
|
pmap_load:
|
|
ld c, 0
|
|
pmap_load_loop:
|
|
push bc
|
|
push ix
|
|
call clear_frame
|
|
pop ix
|
|
pop bc
|
|
ld b, (ix+0)
|
|
ld e, (ix+1)
|
|
ld d, (ix+2)
|
|
push bc
|
|
push ix
|
|
call set_frame
|
|
pop ix
|
|
pop bc
|
|
inc ix
|
|
inc ix
|
|
inc ix
|
|
inc c
|
|
ld a, c
|
|
cp 12
|
|
jp nz, pmap_load_loop
|
|
ret
|
|
|
|
; Stores the pagemap in the memory pointed to by IX
|
|
; The contents of A, BC, DE, and IX are destroyed
|
|
pmap_set:
|
|
ld c, 0
|
|
pmap_set_loop:
|
|
push ix
|
|
call get_frame
|
|
pop ix
|
|
ld (ix+0), b
|
|
ld (ix+1), e
|
|
ld (ix+2), d
|
|
inc ix
|
|
inc ix
|
|
inc ix
|
|
inc c
|
|
ld a, c
|
|
cp 12
|
|
jp nz, pmap_set_loop
|
|
ret
|
|
|
|
RAM_TYPE equ 2
|
|
|
|
; Initializes the virtual memory manager
|
|
vmem_init:
|
|
ld b, RAM_TYPE
|
|
call find_first_card
|
|
ld a, l
|
|
ld c, 15
|
|
ld b, 0
|
|
ld de, vmem_mapping_card
|
|
ld h, d
|
|
ld l, e
|
|
inc de
|
|
ld (hl), a
|
|
ldir
|
|
ld ix, vmem_mapping_bank_low+15
|
|
ld b, 15
|
|
vmem_init_loop:
|
|
ld (ix+0), b
|
|
dec ix
|
|
djnz vmem_init_loop
|
|
ret
|
|
|
|
|
|
|
|
vmem_mapping_card: .ds.b 16, 0
|
|
vmem_mapping_bank_low: .ds.b 16, 0
|
|
vmem_mapping_bank_high: .ds.b 16, 0
|
|
|