Logic operations in 8051 C

Everyone must be familiar with AND(&&), OR(||) and NOT(!) operators in C. well there are also bitwise logical operators also known as AND(&), OR(|), EX-OR(^), Inverter(~), shift right(>>) and shift left(<<).

These bit wise operators are widely used in embedded systems and control.

Bit wise logic operators for C

A	B	A & B	A | B	A ^ B	Y = ~B
0	0	0	0	0	1
0	1	0	1	1	0
1	0	0	1	1
1	1	1	1	0

Used as:

ANDing

0x35 & 0x45 = 0x05

ORing

0x35 | 0x45 = 0x75

XORing

0x35 ^ 0x45 = 0x70

INVERTing

~0x35 = 0xCA

Usage of bit wise shift operation:

Data>>number of bits to be shifted right

Data<<number of bits to be shifted left

0x50>>4 = 0x05

0x45<<2 = 0xB4

An example of logic operation can be seen below.

#include<reg51.h> /*  * issue ascii char to P2 as follows  * P3.1                   P3.0  * 0                         0              send 0  * 0                         1              send 1  * 1                         0              send 2  * 1                         1              send 3  *  */ void main() {                 unsigned char z;                 z = P1;   //read P1                 z = z & 0x03;                 // mask the unused bits                 switch(z)                 {                                 case(0): P2 = '0';                                                  break;                                 case(1): P2 = '1';                                                  break;                                 case(2): P2 = '2';                                                  break;                                 case(3): P2 = '3';                                                  break;                 }// end of switch }// end of main // end of program