PIC instruction!

Nigel Goodwin · Sep 22, 2009

Pommie said:
My aversion to the use of even my (more efficient) macro was the fact it makes the source unreadable. In effect you need a banksel before every memory access. Much better to learn which registers are in which bank and use a single bsf etc to switch banks at the appropriate time. Microchip, in their wisdom, removed all the register addresses from the data sheet sections - EG, timer 1 section.

On a 16F876, using banksel, writing to a tris register can take 6 instructions. This is supposed to be an efficient chip.

I thought your improved macro just inserted the single required BSF? - perhaps I was thinking of someone elses?.

kpatz · Sep 22, 2009

birdman0_o said:
I have no problem memorizing the banks, and if I forget I just check the memory block diagram on the datasheet.

This makes the code more efficient when you know which bank the code is selecting. You can group items in the same bank and perform a function on them before switching back instead of continuous switching between banks.

My macro throws a message in the listing anytime it switches banks, and a different message when it leaves the bank unchanged. That way, once my code is stable, I can make it more efficient by rearranging things to put operations in a common bank together, and I don't have to memorize which bank has what register.

Pommie · Sep 22, 2009

Nigel Goodwin said:
I thought your improved macro just inserted the single required BSF? - perhaps I was thinking of someone elses?.

It does, however, if I don't know which bank something is in I have to do,

Code:

	mysel	TRISA
	movwf	TRISA
	mysel	ANSEL
	clrf	ANSEL
	mysel	ANSELH
	clrf	ANSELH

Yes, the above will assemble efficiently but is just ugly.

Mike.

kpatz · Sep 22, 2009

Pommie said:
It does, however, if I don't know which bank something is in I have to do,

Code:

mysel TRISA movwf TRISA mysel ANSEL clrf ANSEL mysel ANSELH clrf ANSELH

Yes, the above will assemble efficiently but is just ugly.

Mike.

Next time I am up for macro hacking I plan to create macros corresponding to all the register-oriented instructions (e.g. movf/movfw/movwf/bsf/bcf etc.) which will set the bank bits (skipping this if they're already set correctly) and assemble in the instruction in question.

So, instead of Pommie's code above, I could code:

Code:

	mymovwf	TRISA
	myclrf	ANSEL
	myclrf	ANSELH

PIC instruction!

Nigel Goodwin

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PIC instruction!

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