;-----------------------------------------------------------------------------------------
; Execute SPI command. Writes command and two data bytes stored in zero-page locations.
; Reads status and two data bytes and stores back in same locations.
; Set ZP_CMD_PKG before calling, A and X scrambled.
; Uses SPI channel 1 by default, or set channel bits in A and call SPICmd+2
;-----------------------------------------------------------------------------------------

; SPI card commands (assumes slot 4)
SPI_CS		equ $C0C1
SPI_EXEC		equ $C0C0
SPI_DATA		equ $C0C2
SPI_RESET	equ $C0C3

; command and data bytes for spi_cmd
ZP_CMD_PKG	equ $EB	
ZP_CMD_STAT	equ $EB			
ZP_DATAH	equ $EC
ZP_DATAL	equ $ED

SPICmd		lda #$01			; use SPI channel 0 (set bit 0)
		ldx #$00
        		sta SPI_CS		; begin SPI transaction
.nextByte	lda ZP_CMD_PKG,x		; load byte (one command byte, two data bytes)
                	sta SPI_DATA		; store in SPI data latch
                	sta SPI_EXEC		; execute SPI transfer
.wait		lda SPI_CS		; get transfer status
                	bpl .wait		; wait until all 8 bits are sent
                	lda SPI_DATA		; get reply byte from SPI data latch
                	sta ZP_CMD_PKG,x		; store byte (one status byte, two data bytes)
                	inx
                	cpx #$03
                	bne .nextByte		; repeat for all three bytes
               	sta SPI_RESET		; end SPI transaction
                	rts