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.
37 lines
615 B
ArmAsm
37 lines
615 B
ArmAsm
.include "io.inc65"
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.importzp sp, sreg
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.export _uart_txb, _uart_txb_block
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.export _uart_rxb
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.export _uart_status
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.autoimport on
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.code
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; @in A: byte to transmit
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; Transmits a byte over the UART
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_uart_txb:
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sta UART_TXB ; Just write value, don't wait
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rts
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_uart_txb_block:
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pha
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sta UART_TXB ; Write value
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@1: lda UART_STATUS ; Wait for status[0] to be 0
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bit #$01
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bne @1
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pla
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rts
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_uart_rxb:
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lda UART_RXB ; Read value
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ldx #$00
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rts
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_uart_status:
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lda UART_STATUS
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ldx #$00
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rts
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