c6098f2d1f
Eventually I want the kernel to be loaded from the SD card as well, but it still needs to separate from user programs. At some point there should be a folder just for the BIOS, which should read from the boot block of the SD card and start executing, and thats it.
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 |