Function SPIIn(FSR0 As uInteger,Data_bit_mask As uByte,FSR1 As uInteger,clock_bit_mask As uByte,num_bits As uByte)
' SPI (Microwire) Input Routine
'
' Receives up to 16 bits to a serial device, using a data line and a clock line.
'
' Parameters:
' FSR0:			 -> the port to use for the data input, specfied as ADDR(port)
' data_bit_mask: the bit position as a mask (0x01,0x02,0x04,etc) in the port of the data input
' FSR1:	 		 -> the port to use for the clock output, specfied as ADDR(port)
' clock_bit:	 the bit mask in the port of the clock output
' num_bits:		 the number of bits (1 to 16) of data to be sent.
'
' Returns:		 a 16 bit word containing the data received
'
' NOTES:
'		The clock pulse is at least .2 usec long with a 40 mHz PIC clock. The clock code
' 		just toggles the clock pin. 
'		Use #DEFINE SPI_CLOCKUS to make the clock pulse "SPI_CLOCKUS" in length
'       Use #DEFINE SPI_READUS to delay the data read for SPI_READUS us after clock trailing edge
'
'		The shift loop is 14 instructions Long, thus the clock
'		rate is 700 kHz at 40mHz, 350 at 20mHz, etc
'
' 		The user MUST set the clock pin HIGH or LOW initially, depending on the requirements of 
' 		the device. 

	Dim result As uInteger

	result = 0		' Clear out result register
	While num_bits <> 0
	' Assume for now that we want to clock on the trailing edge, and data is in from the left (MSB 1st)
	
		' Generate a clock pulse of at least .2 usec(2 instr at 40 mHz)
		movf	clock_bit_mask,w	' Get the clock port bit
		xorwf	indf1,f				' Toggle clock bit
		'Clock bit length
		#ifdef SPI_CLOCKUS
		pauseus( SPI_CLOCKUS )
		' Since pause destroys WREG, need to reload
		movf	clock_bit_mask,w	' Get the clock port bit
		#else
		nop
		#endif	
		xorwf	indf1,f				' toggle it again
		'Delay to let data settle
		#ifdef SPI_READUS
		pauseus( SPI_READUS )	
		#else
		nop							
		#endif
		' Get a data bit
		movf	indf0,w				' Read the port into W
		andwf	data_bit_mask,w		' mask out the desired bit
		addlw	-1					' Move the bit to the carry bit
		rlcf	result,f			' Shift the carry bit into the LSB
		rlcf	result+1,f			' Shift into the high byte of the word
		num_bits = num_bits - 1
	End While
End Function result

Sub SPIOut(FSR0 As uInteger,Data_bit_mask As uByte,FSR1 As uInteger,clock_bit_mask As uByte,dataout As uInteger,num_bits As uByte)
' SPI (Microwire) Output Routine
'
' Sends up to 16 bits to a serial device, using a data line and a clock line.
'
' Parameters:
' FSR0:	 		 -> the port to use for the data output, specfied as ADDR(port)
' data_bit_mask: the bit position as a mask (0x01,0x02,0x04,etc) in the port of the data output
' FSR1:	 		 -> the port to use for the clock output, specfied as ADDR(port)
' clock_bit:	 the bit mask in the port of the clock output
' data_out:		 a 16 bit word containing the data to be sent, right justfified
' num_bits:		 the number of bits (1 to 16) of data to be sent.
'
' NOTES:
'		The data to be sent should be right-justified in the data word no matter how many bits are being sent,
'		e.g. To send an 8-bit byte containing "10", the Data word should be set up as 0x00001010. The routine
'		will shift the data to the left
'
'		The clock pulse is at least .2 usec long with a 40 mHz PIC clock. The clock code
' 		just toggles the clock pin. 
'		Use #DEFINE SPI_CLOCKUS to make the clock pulse "SPI_CLOCKUS" usec in length
'		Use #DEFINE SPI_WRITEUS to delay the clock by "SPI_WRITEUS" usec after data write

' 		There are 16 instructions in the shift loop, thus at 40 Mhz the clock rate is
'		625 kHz, 312 kHz at 20 mHz, etc
' 		The user MUST set the clock pin HIGH or LOW initially, depending on the requirements of 
' 		the device. 
' 		The data is set up before the clock changes, thus the device can clock in the data
'		on either the leading or trailing edge.

	Dim extra_shifts As uByte, carry As Boolean
	
	extra_shifts = 16 - num_bits	
	While extra_shifts <> 0
		rlcf	dataout,f		' Shift the carry bit into the LSB
		rlcf	dataout+1,f		' Shift into the high byte of the word
		extra_shifts = extra_shifts - 1
	End While
	
	While num_bits <> 0
	' The data is assumed to be right-justified, thus we need to shift the extra (16-num_bits)
	' without sending data to the port
	
		' Rotate the data word into the carry bit. If the carry bit is on, the
		' the data bit to send is a 1
		rlcf	dataout,f		' Shift the carry bit into the LSB
		rlcf	dataout+1,f		' Shift into the high byte of the word
		' Send a data bit to the port
		movf	indf0,w				' Read the port 
		iorwf	data_bit_mask,w		' Set a 1
		btfss	STATUS_C			' Skip if carry on (data bit was 1)
	   	xorwf	data_bit_mask,w		' Data bit was a zero, turn off
	   	' Here is where the port data bit changes
	   	movwf   indf0				' Write back to port
	   	' Delay clock to let data settle
	   	#ifdef SPI_WRITEUS
		pauseus( SPI_WRITEUS )	   	
    	#else
    	nop
    	#endif
		' Generate a clock pulse of at least .2 usec(2 instr at 40 mHz)
		movf	clock_bit_mask,w	' Get the clock port bit
		' Leading edge of clock pulse
		xorwf	indf1,f				' Toggle clock bit
		' Clock bit length
		#ifdef SPI_CLOCKUS
		pauseus( SPI_CLOCKUS )
		' Since pause destroys WREG, need to reload
		movf	clock_bit_mask,w	' Get the clock port bit
		#else
		nop	
		#endif
		' Trailing edge of clock pulse
		xorwf	indf1,f				' toggle it again
		num_bits = num_bits - 1
	End While
End Sub

Function bitposn(count As uByte)
' Given a number (0-7) in count, return a mask  respresenting the position
' of the bit in a byte
' 0: 0x01
' 1: 0x02
	Dim mask As uByte
	'Dim count As uByte
	'movwf	count
	incf	count,f
	movlw	1
loop:
	dcfsnz  count,f
	bra 	finished
	rlcf	wreg,w
	bra		loop
finished:
	movwf   mask,w	
End Function mask