\ SPI Driver                                            

REQUIRED FC!

XASM

MACRO: SO       PORTB 5  MACRO;         \ Data Output

MACRO: SI       PORTB 3  MACRO;         \ Data Input

MACRO: SCK      PORTB 2  MACRO;         \ Clock Output

IN-META

T: SPI-SELECT   M[ BCF PORTB 4 ]M  T;   \ Select line 

T: SPI-DESELECT M[ BSF PORTB 4 ]M  T;

 
: SOFT-SPI-INIT         $10 PORTB C!    \ Set port and direction
                        $CB TRISB C! ;

 
CODE SPI ( b - 'b )
        N 8 D0  RLF (FSR)               \ Get next bit to send
                BCF (FSR) 0             \ Assume bit in is zero
                BCF SO                  \ Assume bit out is zero
                BTFSC STATUS CY         \ Check bit out
                BSF SO                  \ Was one so set out high
                BSF SCK                 \ Set CLK high
                NOP                     \ May need a delay if >4MHz PIC
                BTFSC SI                \ Check SI input
                BSF (FSR) 0             \ Input high so bit in is one
                BCF SCK                 \ Return CLK low
        LOOP    RETURN C;               \ Loop for 8 bits, answer on stack