IBM System/7 Functional Characteristics - All about the IBM 1130 ...

If R=000, specifying the accumulator, this instruction is, in effect, a no-operationbecause the final contents of the accumulator are unchanged from the original contents.Any data ORed with itself has a final result equal to the original data.The carry and overflow indicators are not changed. The result indicators are changedto reflect the final contents of the accumulator.ORing occurs only between corresponding bits in the accumulator and the R register:bit 0 is ORed only with bit 0, bit 1 only with bit 1, and so on. The four possibleORing combinations are:Bit Value fromIndex RegisterBit Value fromAccumulator0 0 00 1 11 0 11 1 1Result inAccumulatorThus, a bit value of 1 will result in the accumulator if a corresponding bit positionis set to a value of 1 in either the accumulator or the register (R). If the bit positionsin both the accumulator and the R register ale set to a value of 1, the ORcondition is still satisfied, so the corresponding result bit is set to a 1 in theaccumulator.Example:Word in accumulator 0011 0101 1111 1010Word in index register 0101 0001 1010 0000Result in accumulator 0111 0101 1111 1010Exclusive OR Register (PXR)0 5 8 15Op code R Modifier1 1 1 1 1 X X X 0 0 0 0 1 0 1 0 1I I I I I I 1 1 1 1 1F 8-F 0 5The contents of the accumulator are exclusive ORed, bit by bit, with the contents of theregister (R). The result replaces the contents of the accumulator. When R specifies anindex register, the contents of the addressed index register are not changed.An R field of 000, which specifies the accumulator, is a simple method of clearing theaccumulator. Any data that is exclusive ORed with itself results in setting all the bitsto O's.The carry and overflow indicators are not changed. The result indicators are changedto reflect the final contents of the accumulator.Processor Instructions 4-23