.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