Doubt in the rotation asm pic16F

[aless2056]

Guys, I'm a beginner and I'm in doubt in the RRF Rotation instruction. Assuming I have this value

0000 0011 0011 1100
AH = 0000 0011
AL = 0011 1100

Did I do that?

RRF AH, F
RRF AL, F
RRF AH, F
RRF AL, F

Will the result be?

AH = 0000 0000
AL = 1100 1111

 

[KlausST]

Hi,

The answer is: it depends.

I don't want to do your homework.
So please show the states after each commend. Step by step.


Klaus

 

[betwixt]

You should study the data sheet, it explains all the instructions and gives examples.

'AH' and 'AL' presumably are register names and independent 8-bit values.
RRF AH, F AH is 0000 0011 before the instruction so rotating it right through the carry flag, bit 7 = whatever was in C, and C becomes what was in Bit 0
The same applies to the AL register but note there is only one carry bit so it may transfer a bit from one register to the next.

We can't predict what the result will be without knowing what was in C at the outset.

Brian.

 

[FvM]

C must be cleared before executing RRF AH, e.g. with CLRF STATUS.

 

[KlausST]

Hi,

... or filled with the LSB of AL for a true rotation...

Klaus