202 lines
3.2 KiB
ArmAsm
202 lines
3.2 KiB
ArmAsm
.importzp sp, ptr1, ptr2, ptr3, ptr4, tmp1, tmp2, tmp3, sreg
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.autoimport on
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.feature string_escapes
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.MACPACK generic
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.MACPACK longbranch
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_console_clear = $0
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_console_read_char = $2
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_console_write_char = $4
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_sd_readblock = $6
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sectors_per_cluster = $800D
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reserved_sectors = $800E
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fat_count = $8010
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sectors_per_fat = $8024
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buf = $8200
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addrh = $0000
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addrl = $0000
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.segment "BOOTSECTOR"
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_start:
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jmp _main
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.byte "SUPR6502"
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_preamble:
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.res (11+_start-_preamble)
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_bpb: .res 60
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_main:
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lda #<str
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ldx #>str
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jsr _cputs
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lda #<_addr
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ldx #>_addr
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jsr pushax
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lda fat_count
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cmp #$2
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jne @fail
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lda sectors_per_fat
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asl
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pha
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lda sectors_per_fat + 1
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rol
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tax
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pla
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adc reserved_sectors
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bcc @a
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inx
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@a: jsr pushax
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stz sreg
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stz sreg+1
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jsr pusheax
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lda #<buf
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ldx #>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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lda #<buf
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ldx #>buf
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jsr _SD_printBuf
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lda #$20
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sta ptr3
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lda #$82
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sta ptr3 + 1
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ldy #$0b
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@1: lda (ptr3),y
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cmp #$0f
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bne @2
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clc
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lda ptr3
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adc #$20
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sta ptr3
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bra @1
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@2: ldy #11
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lda #$00
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sta (ptr3),y
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lda ptr3
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pha
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ldx ptr3 + 1
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phx
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lda #<_boot2_str
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ldx #>_boot2_str
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jsr pushax
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plx
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pla
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jsr _strcmp
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bne @fail
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lda #<_good
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ldx #>_good
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jsr _cputs
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ldy #$1b
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lda (ptr3),y
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tax
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dey
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lda (ptr3),y
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sec
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sbc #$02 ; don't handle carry, assume <256
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; now a is the cluster num minus 2. We need to multiply this by
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; 8 and add it to 0x77f0
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; multiply by 8 is asl3
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ldx #$77
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asl
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asl
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asl
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clc
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adc #$f0
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bcc @3
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inx
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@3: pha
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phx
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lda #$00
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sta sreg
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lda #$00
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sta sreg+1
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plx
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pla
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phx
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pha
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jsr pusheax
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lda #<buf
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ldx #>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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lda #$00
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sta sreg
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lda #$00
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sta sreg+1
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pla
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plx
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inc
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jsr pusheax
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lda #<buf
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ldx #>buf
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inx
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inx
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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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jmp buf
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bra @end
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; Now we have the cluster number of the bootloader (3)
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; this means we need to read from address 00ef_e000 + ((3 -2) * 8 * 512)
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; 00eff000 is the address we want, which is efe000 + 4096
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@fail: lda #<_fail
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ldx #>_fail
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jsr _cputs
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@end: bra @end
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str: .asciiz "boot\r\n"
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_boot2_str: .asciiz "BOOT2 BIN"
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_fail: .asciiz "not bootloader\r\n"
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_good: .asciiz "found bootloader!\r\n"
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_cluster: .asciiz "cluster: %lx\r\n"
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_addr: .asciiz "addr: %x\r\n"
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_end:
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.res (440+_start-_end)
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.res 6
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.res 16
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.res 16
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.res 16
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.res 16
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.byte $55
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.byte $AA
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