122 lines
2.3 KiB
ArmAsm
122 lines
2.3 KiB
ArmAsm
.MACPACK generic
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.autoimport
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.feature string_escapes
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.importzp ptr1, sreg
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.import _SD_readSingleBlock
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.export _fat32_init
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.data
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root_cluster: .res 4
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fat_start_sector: .res 2
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data_start_sector: .res 4
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fat_size: .res 4
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sd_buf: .res 512
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data_start_sect_str: .asciiz "Data sector start: 0x%lx\n"
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starting_cluster_str: .asciiz "Root cluster num: %lx\n";
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value_str: .asciiz "Value: 0x%x\n"
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.code
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bytes_per_sector = sd_buf + $0B
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sectors_per_cluster = sd_buf + $0D
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reserved_sectors = sd_buf + $0E
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fat_count = sd_buf + $10
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sectors_per_fat = sd_buf + $24
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root_cluster_offs = sd_buf + $2C
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.proc _fat32_init
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; load sector 0 into sd_buf
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lda #$00
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ldx #$00
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stz sreg
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stz sreg+1
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jsr pusheax
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lda #<sd_buf
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ldx #>sd_buf
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jsr pushax
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lda #<ptr1
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ldx #>ptr1
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jsr _SD_readSingleBlock
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ldx #$00
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L1: lda root_cluster_offs,x
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sta root_cluster,x
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inx
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cpx #$4
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blt L1
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; Multiply reserved sectors and bytes per sector, then divide by 512 to get sd sectors
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lda reserved_sectors
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jsr pusha0
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lda bytes_per_sector
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ldx bytes_per_sector+1
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jsr _imulii
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txa
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lsr
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sta fat_start_sector
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stz fat_start_sector + 1
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; multiply fat size and number of fats to get total fat size
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lda fat_count
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jsr pusha0
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lda sectors_per_fat
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ldx sectors_per_fat+1
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jsr _lmulii
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sta fat_size
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stx fat_size+1
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lda sreg
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sta fat_size+2
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lda sreg+1
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sta fat_size+3
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; Add fat size to starting fat sector to get data start sector
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lda fat_size
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adc fat_start_sector
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sta data_start_sector
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lda fat_size+1
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adc fat_start_sector+1
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sta data_start_sector+1
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lda fat_size+2
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sta data_start_sector+2
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lda fat_size+3
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sta data_start_sector+3
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lda #<data_start_sect_str
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ldx #>data_start_sect_str
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jsr pushax
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lda data_start_sector+2
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sta sreg
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lda data_start_sector+3
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sta sreg+1
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lda data_start_sector
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ldx data_start_sector+1
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jsr pusheax
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ldy #$6
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jsr _cprintf
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; load sector <data_start> into sd_buf
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lda data_start_sector+2
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sta sreg
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lda data_start_sector+3
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sta sreg+1
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lda data_start_sector
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ldx data_start_sector+1
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jsr pusheax
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lda #<sd_buf
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ldx #>sd_buf
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jsr pushax
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lda #<ptr1
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ldx #>ptr1
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jsr _SD_readSingleBlock
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rts
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.endproc
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