f3c7ac9696
Instead of using the bootsector to load a bootloader, just put the bootloader in the ROM and call it a day. It looks for a file on the SD card in the root directory named `kernel.bin` and loads it into memory. This is not a perfect solution, as the kernel will grow larger and the kernel load address will have to change. At this point I could add back the bootloader, but that is for later. Also the bootloader is just a copy of the kernel, so that can be trimmed down a lot.
66 lines
1.1 KiB
ArmAsm
66 lines
1.1 KiB
ArmAsm
.include "io.inc65"
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.importzp sp, sreg, ptr1
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.export _sd_card_command
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.export _sd_card_resp
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.export _sd_card_read_byte
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.export _sd_card_wait_for_data
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.autoimport on
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.code
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; Send sd card command.
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; command is in A register, the args are on the stack
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; I think the order is high byte first?
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_sd_card_command:
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pha
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jsr popeax
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sta SD_ARG
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stx SD_ARG+1
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lda sreg
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sta SD_ARG+2
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lda sreg+1
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sta SD_ARG+3
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pla
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sta SD_CMD
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rts
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; void sd_card_resp(uint32_t* resp);
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_sd_card_resp:
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phy
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sta ptr1 ; store pointer
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stx ptr1+1
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@1: lda SD_CMD ; wait for status flag
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and #$01
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beq @1
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lda SD_ARG
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ldy #$0
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sta (ptr1),y
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lda SD_ARG+1
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iny
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sta (ptr1),y
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lda SD_ARG+2
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iny
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sta (ptr1),y
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lda SD_ARG+3
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iny
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sta (ptr1),y
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ply
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rts
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_sd_card_read_byte:
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lda SD_DATA
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ldx #$00
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rts
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_sd_card_wait_for_data:
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pha
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@1: lda SD_CMD ; wait for status flag
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and #$02
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beq @1
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pla
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rts |