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

Exclusive ORing occurs only between corresponding bits in the accumulator and thespecified register: bit 0 is exclusive ORed only with bit 0, bit 1 only with bit 1, andso on. The four possible exclusive-ORing combinations are:Bit Value fromIndex RegisterBit Value fromAccumulator0 0 00 1 11 0 11 1 0Result inAccumulatorThus, a bit value of 1 will result in the accumulator only if a corresponding bit positionis set to a value of 1 in the accumulator or in the register (R), but not both.Example:Word in accumulator 0110 1100 0000 1111Word in index register 11 00 0011 0000 1111Result in accumulator 1010 1111 0000 0000SHIFT INSTRUCTIONSShift instructions shift data, bit by bit, to the right or to the left. The shift operationcan be performed on data residing in either an index register or the accumulator. Allshift instructions have the same operation code in bits 0 to 4. A particular shift operationis specified by the modifier bits (bits 8 to 10) of the shift instruction.The manner of shifting depends on the particular shift instruction. In shift-leftoperations, bits that are shifted into the low-order vacated position can be:1. Zeros—a logical left shift (PSLL instruction).2. Bits that are shifted out of the high-order position (bit 0) of the shiftedregister—a circular left shift (PSLC instruction).For example:Original operand in accumulator1111 0000 1111 1011OAfter a logical shift left of one position1110 0001 1111 0110 –4-- Zero shifted inL High-order bitvalue shifted outIn shift-right operations, bits that are shifted into the vacated high-order position can be:1. Zeros—a logical right shift (PSRL instruction).2. The original value of the sign bit (bit 0 of the shifted register)—an arithmetic rightshift (PSRA instruction).4-24 GA34-0003