m (Typo fix.)
Revision as of 23:25, 5 August 2011
|Function||Logically Exclusive OR two values|
EOR will perform a logical, bitwise, Exclusive OR between the two operands, placing the result in the destination register; this is useful for inverting 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 (ANDS), 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.
EOR is useful for inverting bits in a bitfield. For each bit, EORing with 1 will invert the bit, and EORing with 0 will leave it as it was.
This instruction is the same as the one called XOR on some other platforms.
EOR<suffix> <dest>, <op 1>, <op 2>
dest = op_1 EOR op_2
EOR sets the result bit upon either, but not both of the input bits being the same.
|op_1 bit||op_2 bit||Result bit|
EOR R0, R0, #3 ; Invert bits zero and one of R0. EORS R0, R0, #3 ; As above, but also updates status flags
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||0 0 0 1||S||op_1||dest||op_2/shift|
Note: If the I bit is zero, and bits 4 and 7 are both one (with bits 5,6 zero), the instruction is MLA, not EOR.