In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bfranke wrote:

For anyone who might be slightly curious how this turned out. . .  I never was able to get the timer to work properly using the "Software Timer Mode".  I finally changed my method and got what I intended all along, without the timer.  It's actually better this way.  I'm just glad I can move on now.

But there is a curious thing here.  I have to put a NOP right before the RETI or it doesn't work right for me.  I believe this is due to pipeline issues since the last thing I do is write to the port register, but I'm not sure.  Anyway, I posted the code for my interrupt in case anyone else has experienced this same thing or can explain why a NOP would be needed there.

Thanks,

Bill

org	$10
				;$10 should be available. fifo never actually uses it.			
FIFO		= $
		ds 9
Temp 		ds 1
BitPointer	ds 1		; this is the bit pointer for each byte (8 max);
FifoPointer	ds 1		; this is the current byte
BitWaste	ds 1		; needed to get rid of non-data clock pulses in interupt and final pass
WasteClk	ds 1		; same
VoltBits	ds 1

org	$000
;---------------------------------------------------
; ISR
; FIFO interupt - Triggers off the clock pulse (Port 'A' pin '7') and captures the data (Port 'A' pin '8')
; after a 36 count display flash is complete and captured, this transfers the final 4 bytes into another
; 4 bytes that are read by FifoSend
;---------------------------------------------------
		bank	$10
		inc	BitWaste
		stc
		cjb	BitWaste,WasteClk,FillPointerRet	; we want to loose the first 3 clock pulses (they have no data)
		mov	w, #FIFO	; indirect address the FIFO memory
		add	w, FifoPointer	; FIFO pointer
		mov	fsr, w
		movb	c,rb.7		; capture the data into carry
		rl	ind		; rotate c into the current FIFO		
		dec	BitPointer
		snz
		jmp	FillPointer
FillPointerRet
		mov	w,#$19		; enable pending reg.
		mov	m,w
		mov	!rb,#%10111111	; clear the pending register so we can do this again.
		[purple]nop	; needed apparently because of pipeline problems[/purple]
		reti

FillPointer
		mov	BitPointer, #8
		dec	FifoPointer
		sz
		jmp	FillPointerRet
		mov	BitWaste, #$FF	; have to waste the final bit also
		mov	FifoPointer, #4	; use this variable temporarily as a loop counter
:loop
		mov	w, #FIFO	; indirect address the FIFO memory
		add	w, FifoPointer
		mov	fsr, w
		mov	Temp, ind	; temporarily save the value
		add	fsr, #4		; incr 4
		mov	ind, Temp	; store it
		decsz	FifoPointer
		jmp	:loop		; loop four times	
		mov	FifoPointer, #4
		jmp	FillPointerRet

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