; -*-asm-*-
include(`common.m4')

        BRA r :reset ; RESB
        BRA r :irq   ; IRQB

irq:    PHA s
        LDA a %10000000
        STA a IFR
        PLA s
        RTI s

        ;; reset stack
reset:  SEI i

        LDX # ff
        TXS i

        ;; xxxSSSxx
        LDA # hh(ACR_SR_OUT_PHI2)
        STA a ACR

        LDA # %10000000
        STA a PORTA

        ;; CS SCLK DO x x x x x
        LDA # %11100000
        STA a DDRA

        ;; LDA # %01111111
        ;; STA a IER

        ;; LDA # %10000100
        ;; STA a IER

        ;; low byte
        LDX # %11000000         ; write conf
        LDY # %00000001
        JSR a :spi16

        LDX # %10000000         ; write data
        LDY # ca
        JSR a :spi16

forever: BRA r :forever

        ;; CS low
spi16:  LDA # %00000000
        STA a PORTA

        STX zp 1
        STY zp 2

        LDY # 2
_spi_next:      LDX # 8
                CLC i
                ASL zp,y 0
                LDA # %00000000 ; clear DO
                BCC r :_spi_z
                ORA # %00100000 ; set DO
_spi_z:         STA a PORTA
                NOP i
                ORA # %01000000 ; set SCLK
                STA a PORTA
                AND # %10111111 ; clear SCLK
                STA a PORTA
                DEX i
                BNE r :_spi_next
                DEY i
                BNE r :_spi_next
        ;; CS high
        LDA # %10000000
        STA a PORTA
        RTS s