Change MSB and LSB

Actually google can very useful in cases like this one:

http://www.google.com/search?hl=en&ie=UTF-8&q=reverse+bits+byte&btnG=Google+Search

Just one of the results:

http://www.semiconductors.philips.com/acrobat/applicationnotes/AN709.pdf

- mike

I would be tempted to try something like the following (I can't try it now because I am at a location without access to my Keil toolchain).

static unsigned char bdata src_byte;
static unsigned char bdata dst_byte;

static sbit src_bit0 = src_byte ^ 0;
static sbit src_bit1 = src_byte ^ 1;
static sbit src_bit2 = src_byte ^ 2;
static sbit src_bit3 = src_byte ^ 3;
static sbit src_bit4 = src_byte ^ 4;
static sbit src_bit5 = src_byte ^ 5;
static sbit src_bit6 = src_byte ^ 6;
static sbit src_bit7 = src_byte ^ 7;

static sbit dst_bit0 = dst_byte ^ 0;
static sbit dst_bit1 = dst_byte ^ 1;
static sbit dst_bit2 = dst_byte ^ 2;
static sbit dst_bit3 = dst_byte ^ 3;
static sbit dst_bit4 = dst_byte ^ 4;
static sbit dst_bit5 = dst_byte ^ 5;
static sbit dst_bit6 = dst_byte ^ 6;
static sbit dst_bit7 = dst_byte ^ 7;

unsigned char reverse_bits(unsigned char b)
{
    src_byte = b;

    dst_bit0 = src_bit7;
    dst_bit1 = src_bit6;
    dst_bit2 = src_bit5;
    dst_bit3 = src_bit4;
    dst_bit4 = src_bit3;
    dst_bit5 = src_bit2;
    dst_bit6 = src_bit1;
    dst_bit7 = src_bit0;

    return dst_byte;
}

    MOV C,src_bit7
    MOV dst_bit0,C
    ; ...

Thank you - the app note is very helpful

"...the app note..."

Oops, sorry. I had taken your product selection of C51 to mean that you were targeting an 8051 and its instruction set, not an XA.

The bfastest, simplest, most elegant way is a lookup table
unsigned char code{}={0, 0x08, 0x40....

Erik

I found a other simple way

(17 Byte & 17 Cycle)

	MOV C, ACC.1		;1 76543210
	RLC A			;7 65432101
	MOV ACC.2, C		;7 65432701
	MOV C, ACC.3		;2 65432701
	RLC A			;6 54327012
	MOV ACC.4, C		;6 54367012
	MOV C, ACC.5		;3 54367012
	RLC A			;5 43670123
	MOV ACC.6, C		;5 45670123
	SWAP A			;5 01234567

"I found a other simple way"

Hey, no fair! You didn't say we could use assembly ;-)

Nobody said you couldn't...

Toolset = C51
Criterion = "esay" (easy, and the only criterion stated)

Given all the posts asking about the SRC directive, assembly modules callable from C, C modules callable from assembly, etc., who would have though that:

easy = assembly

How silly of me!

Hmm... I suppose "easy" is somewhat subjective, really? l;-)

"It takes a lot of effort to make something appear effortless"