Rotating 8-bit variables in CodeVisionAVR

[hegazyelm3lm]

rotating variables in C

Hi i am using CodeVisionAVR i want to rotate 8-bit variables, can anyone help me?

 

[asahin11]

Re: rotating variables in C

hi hegazyelm3lm,

I dont know CodeVisionAVR but on C you can use << or >> operator to rotate left or right. For example;

i << 1 : rotate i to left one bit
i >> 2 : rotate i to right two bit

regrads,

 

[Rooftop]

Re: rotating variables in C

hi all,

Emm i'm not sure but isn't >> just shift, not rotate?

I'm using keill and if i write

a = a >> 1;

then it means a will be shifted to right once and if i write

a = a << 2;

then it means a will be shifted to left twice.

I dunno it's different or not but in Keill it's just shift not rotate
Anyway i'm looking for how to rotate right or left too
That's all

thanks a lot

 

[checkmate]

Re: rotating variables in C

The <</>> are shift operators, not rotate operators. This applies on all variants of C I have ever come across.

In C, you can do this

new=(old & 0x01)?((old>>1) | 0x80)old>>1)

I'm not an AVR user, but I'm pretty sure that they have rotate in their ISA. Then the optimal method is to do an inline ASM.

 

[amrstaha]

Try this:
x=(x<<1)|(x>>7);
this will rotate the byte x one bit position to the left.
x=(x>>1)|(x<<7);
and this will rotate it to the right.
Good luck.