101 lines
2.0 KiB
ArmAsm
101 lines
2.0 KiB
ArmAsm
.MACPACK generic
|
|
|
|
.autoimport
|
|
.feature string_escapes
|
|
|
|
.importzp ptr1, sreg
|
|
|
|
.import _SD_readSingleBlock
|
|
|
|
.export _fat32_init
|
|
|
|
.export _root_cluster, _fat_start_sector, _data_start_sector
|
|
.export _fat_size, _sd_buf, _sectors_per_cluster
|
|
|
|
|
|
.data
|
|
_root_cluster: .res 4
|
|
_fat_start_sector: .res 2
|
|
_data_start_sector: .res 4
|
|
_fat_size: .res 4
|
|
_sectors_per_cluster: .res 1
|
|
|
|
_sd_buf: .res 512
|
|
|
|
data_start_sect_str: .asciiz "Data sector start: 0x%lx\n"
|
|
starting_cluster_str: .asciiz "Root cluster num: %lx\n";
|
|
value_str: .asciiz "Value: 0x%x\n"
|
|
|
|
.code
|
|
|
|
bytes_per_sector = _sd_buf + $0B
|
|
sectors_per_cluster = _sd_buf + $0D
|
|
reserved_sectors = _sd_buf + $0E
|
|
fat_count = _sd_buf + $10
|
|
sectors_per_fat = _sd_buf + $24
|
|
root_cluster_offs = _sd_buf + $2C
|
|
|
|
.proc _fat32_init
|
|
; load sector 0 into sd_buf
|
|
lda #$00
|
|
ldx #$00
|
|
stz sreg
|
|
stz sreg+1
|
|
jsr pusheax
|
|
lda #<_sd_buf
|
|
ldx #>_sd_buf
|
|
jsr pushax
|
|
lda #<ptr1
|
|
ldx #>ptr1
|
|
jsr _SD_readSingleBlock
|
|
|
|
lda sectors_per_cluster
|
|
sta _sectors_per_cluster
|
|
|
|
ldx #$00
|
|
L1: lda root_cluster_offs,x
|
|
sta _root_cluster,x
|
|
inx
|
|
cpx #$4
|
|
blt L1
|
|
|
|
; Multiply reserved sectors and bytes per sector, then divide by 512 to get sd sectors
|
|
lda reserved_sectors
|
|
jsr pusha0
|
|
lda bytes_per_sector
|
|
ldx bytes_per_sector+1
|
|
jsr _imulii
|
|
txa
|
|
lsr
|
|
sta _fat_start_sector
|
|
stz _fat_start_sector + 1
|
|
|
|
; multiply fat size and number of fats to get total fat size
|
|
lda fat_count
|
|
jsr pusha0
|
|
lda sectors_per_fat
|
|
ldx sectors_per_fat+1
|
|
jsr _lmulii
|
|
sta _fat_size
|
|
stx _fat_size+1
|
|
lda sreg
|
|
sta _fat_size+2
|
|
lda sreg+1
|
|
sta _fat_size+3
|
|
|
|
|
|
; Add fat size to starting fat sector to get data start sector
|
|
lda _fat_size
|
|
adc _fat_start_sector
|
|
sta _data_start_sector
|
|
lda _fat_size+1
|
|
adc _fat_start_sector+1
|
|
sta _data_start_sector+1
|
|
lda _fat_size+2
|
|
sta _data_start_sector+2
|
|
lda _fat_size+3
|
|
sta _data_start_sector+3
|
|
|
|
rts
|
|
.endproc
|