Adding data to an "array" in ASM

[The Master]

Theres 2 reasons.

1) For a while now ive been wanting to learn ASM. By learning ASM a lot of things in other languages like PBP and even C are starting to make sense. I think its a very usefull thing to learn. It helps to understand how things are actually working inside the chip

2) Probably the most important one. This section of code is only part of a much bigger program. Its actually the same one from my other thread which is titled "PBP Using too many instructions". ASM uses a lot less instructions so i can finally add in the extra features that i wanted to do in PBP but couldnt because the code was running too slow.

[The Master]

Im having a bit of trouble getting this code working.

Heres some test code i wrote

	MOVLW	38
	MOVWF	FSR0
	
	MOVLW	57
	MOVWF	38
	MOVFF	INDF0,TXREG

This code should set W to 38 then move that value to FSR0.

It then sets W to 57 (my test value) and moves W to memory location 38. Then it sends INDF0 over serial to the PC. I would expect INDF0 to reference memory location 38 and send 57 but it doesnt. I keep getting random values (a different one each time i reset the PIC asif its an uninitialized memory location). Its not a serial problem. MOVWF TXREG sends the correct value.

I know im writing data to memory location 38 and if i read FSR0 back it also says 38. Did i miss something obvious? It seems like both are accessing memory location 38 but in 2 different blocks of memory (im not sure if thats possible)

[Darrel Taylor]

FSR0 is a constant that equates to 0.
It's for use with the LFSR opcode, LFSR FSR0, 38

The address for the FSR0 is 2 bytes, FSR0L and FSR0H.
So with your example, it could be one of these ...

	LFSR  FSR0, 38
	
	MOVLW	57
	MOVWF	38
	MOVFF	INDF0,TXREG

... OR ...

	MOVLW	38
	MOVWF	FSR0L
	CLRF	FSR0H
	
	MOVLW	57
	MOVWF	38
	MOVFF	INDF0,TXREG

hth,

[The Master]

Thanks. Thats working perfectly now