[SOLVED] reverse a binary number

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Marvin_G

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what is the simplest code to reverse a binary number in c? like 11110000 --> 00001111..i got 1 but its quite long..mind to share ur idea? ^^
 

use shift operator I mean right shift or left shift >> or <<

Good Luck
 

A lookup table, this was suggested by FvM in an older post about FPGA I think but it applies to mcu too.

The fastest way would be to use 8bit lookup table but you need 256 bytes of data.
I have used a 4bit lookup table that makes the conversion in two steps with just 16bytes for the lookup table, it is the best compromise I think.

See the 8 and 16bit functions 8/16 bit value reverting function (11000000 to 00000011) - Blogs - Forum for Electronics

Alex
 

u have to rotate the bits so.... but not just shift...

to rotate a byte by n bits to the right:

a = (a >> n) || (a << (8-n))

you probably want to make your code more general (don't hardcode '8').​
 

For 8051 MCUs:

....
....
MOV A, byte
MOV counter, #8
LOOP:
RLC A
XCH A, temp
RRC A
XCH A, temp
DJNZ counter, LOOP
....
....

The register "temp" holds the inverse of "byte"

Kerim
 
Last edited:

thanks guys for your idea..^^

---------- Post added at 04:06 ---------- Previous post was at 04:05 ----------
KerimF said:
For 8051 MCUs:

....
....
MOV A, byte
MOV counter, #8
LOOP:
RLC A
XCH A, temp
RRC A
XCH A, temp
DJNZ counter, LOOP
....
....

The register "temp" holds the inverse of "byte"

Kerim
Click to expand...

hye there..tanks for ur code but i wanted it in c..
 

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