compound bitwise OR (|=)
Description
The compound bitwise OR operator (|=) is often used with a variable and a constant to “set” (set to 1) particular bits in a variable.
Syntax
x |= y; // equivalent to x = x | y;
Parameters
x: a char, int or long variable
y: an integer constant or char, int, or long
Example
First, a review of the Bitwise OR (|) operator
0 0 1 1 operand1
0 1 0 1 operand2
———-
0 1 1 1 (operand1 | operand2) – returned result
Bits that are “bitwise ORed” with 0 are unchanged, so if myByte is a byte variable,
myByte | B00000000 = myByte;
Bits that are “bitwise ORed” with 1 are set to 1 so:
myByte | B11111111 = B11111111;
Consequently – to set bits 0 & 1 of a variable, while leaving the rest of the variable unchanged, use the compound bitwise OR operator (|=) with the constant B00000011
1 0 1 0 1 0 1 0 variable
0 0 0 0 0 0 1 1 mask
----------------------
1 0 1 0 1 0 1 1
variable unchanged
bits set
Here is the same representation with the variables bits replaced with the symbol x
x x x x x x x x variable
0 0 0 0 0 0 1 1 mask
----------------------
x x x x x x 1 1
variable unchanged
bits set
So if:
myByte = B10101010;
myByte |= B00000011 == B10101011;
See also
－ &= (compound bitwise and)
－ & (bitwise AND)
－ | (bitwise OR)
The text of the 86Duino reference is a modification of the Arduino reference, and is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.
