PIC18 to PIC16 asm instructions

[augustinetez]

I know there used to b a 16F to 18F migration document on the Microchip website at one stage, but I'm buggered if I can find anything on that site anymore.

So quick (dumb-ish) question - is RRCF in 18F asm the same as RRF in 16F asm?

Reading the datasheets seems to indicate it is, just want to make sure I'm not missing something.

As for why do I want to know - converting this to use in a 12F chip:-

16-bit random generator (tested)

The 0xA1 is part of a prime polynom value 0xA1A1 which generates a full LFSR

Random:
    BCF     STATUS,C   
    RRCF    LFSRVALUEH,F
    RRCF    LFSRVALUEL,F
    BTFSS   STATUS,C
    RETURN
    MOVLW   0xA1
    XORWF   LFSRVALUEH
    XORWF   LFSRVALUEL   
    RETURN

 

[Diver300]

So quick (dumb-ish) question - is RRCF in 18F asm the same as RRF in 16F asm?

It's not a dumb question, they are the same.

I think that the name RRCF, Rotate Right f through Carry, is to distinguish it from RRNCF, Rotate Right f (No Carry).

RRNCF has no equivalent in 16F asm, so there the RRF just means Rotate Right f through Carry.

RRNCF would be incorrect in your code as the carry bits wouldn't do anything and the code would always return with the carry bit clear.

 

[augustinetez]

Thanks Diver, I'll plug it in tomorrow and see if it does what I want.

 

[MaxHeadRoom78]

The Pseudo commands also appear to still work in the latest Pic's.

List of pseudo mnemomics understood by MPASM

List of pseudo mnemomics understood by MPASM

www.piclist.com

 

[Pommie]

You can mimic RRNCF in pic16 by doing,
RRF file,w
RRF file,f
first instruction moves bit 0 into carry and the second moves the file content and moves bit 0 into bit 7.
Not relevant to this question but may be useful down the line.

Mike.