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