Rotate left

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Jan Lichtenbelt
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Location: Haren GN, the Netherlands
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Rotate left

Post by Jan Lichtenbelt »

Is there a C-code for rotate left and rotate right?

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Benj
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Re: Rotate left

Post by Benj »

Hi Jan,

By rotate do you mean shift or do you need the bits to wrap around?

Here is some code to shift.

Code: Select all

var = var >> 1;
If you want to shift and wrap then you will likely have to do something like this.

Code: Select all

count = 0;
while (count < shiftcount)
{
bitsave = var & 0x01;
var = var >> 1;

if (bitsave == 0x01)
 var = var | 0x80;

count = count + 1;
}
Or to go the other way.

Code: Select all

count = 0;
while (count < shiftcount)
{
bitsave = var & 0x80;
var = var << 1;

if (bitsave == 0x80)
 var = var | 0x01;

count = count + 1;
}

User avatar
Jan Lichtenbelt
Posts: 796
Joined: Tue Feb 17, 2009 8:35 pm
Location: Haren GN, the Netherlands
Contact:

Re: Rotate left

Post by Jan Lichtenbelt »

I think the sortest way to rotate left of the variable Ab will be:

asm MOVF gbl_FCV_AB, F
asm RLF gbl_FCV_AB, F

and rotate right:
asm MOVF gbl_FCV_AB, F
asm RRF gbl_FCV_AB, F

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