ORR

ORR

Instruction	ORR[S]
Function	Logically OR two values
Category	Data processing
ARM family	All
Notes	-

ORR[S] : bitwise OR

ORR will perform a logical, bitwise, OR between the two operands, placing the result in the destination register; this is useful for setting certain bits. Operand 1 is a register, operand 2 can be a register, shifted register, or an immediate value (which may be shifted. If the S bit is set (ORRS), the N and Z flags are set according to the result, the C flag is set according to the shift (if used), and the V flag remains unaltered.

ORR is useful for setting bits in a bitfield. For each bit, ORRing with 1 will set the bit, and ORRing with 0 will leave it as it was.

Syntax

  ORR<suffix>  <dest>, <op 1>, <op 2>

Function

  dest = op_1 OR op_2

ORR sets the result bit upon both of the input bits being the same.

Truth table:

op_1 bit	op_2 bit	Result bit
0	0	0
0	1	1
1	0	1
1	1	1

Example

  ORR  R0, R0, #3  ; Set bits zero and one of R0.

Technical

The instruction bit pattern is as follows:

31 - 28	27	26	25	24 - 21	20	19 - 16	15 - 12	11 - 0
condition	0	0	I	1 1 0 0	S	op_1	dest	op_2/shift