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

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

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

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An R field of 000 means that <strong>the</strong> effective address of <strong>the</strong> storage data is generatedusing <strong>the</strong> IAR as <strong>the</strong> base register.The carry and overflow indicators are not changed. The result indicators are changed toreflect <strong>the</strong> final contents of <strong>the</strong> accumulator.ORing occurs only between corresponding bits in <strong>the</strong> accumulator and <strong>the</strong> storage word:bit 0 is ORed only with bit 0, bit 1 only with bit 1, and so on. The four possible ORingcombinations are:Bit Value fromStorage WordBit Value fromAccumulator0 0 00 1 11 0 11 1 1Result inAccumulatorThus, a bit value of 1 will result in <strong>the</strong> accumulator if a corresponding bit position isset to a value of 1 in ei<strong>the</strong>r <strong>the</strong> accumulator or <strong>the</strong> storage word. If <strong>the</strong> bit positionsin both <strong>the</strong> accumulator and <strong>the</strong> storage word are set to a value of 1, <strong>the</strong> OR condition isstill satisfied, so <strong>the</strong> corresponding result bit is set to a 1 in <strong>the</strong> accumulator.Example:Word in accumulatorWord from storageResult in accumulator0011 0101 1111 10100101 0001 1010 00000111 0101 1111 1010Exclusive OR (PX)0 5 815Op code R1 1 1 1 0 X X XI IDisplacementF 0-7 X XThe contents of <strong>the</strong> accumulator are exclusive ORed, bit by bit, with <strong>the</strong> contents of <strong>the</strong>storage location specified by <strong>the</strong> effective address. The result replaces <strong>the</strong> contents of<strong>the</strong> accumulator. The contents of <strong>the</strong> addressed storage word are not changed.An R field of 000 means that <strong>the</strong> effective address of <strong>the</strong> storage data is generatedusing <strong>the</strong> IAR as <strong>the</strong> base register.The carry and overflow indicators are not changed. The result indicators are changed toreflect <strong>the</strong> final contents of <strong>the</strong> accumulator.Exclusive ORing occurs only between corresponding bits in <strong>the</strong> accumulator and <strong>the</strong>storage word: bit 0 is exclusive ORed only with bit 0, bit 1 only with bit 1, and soon. The four possible exclusive-ORing combinations are:Bit Value fromStorage WordBit Value fromAccumulator0 0 00 1 11 0 11 1 0Result inAccumulatorThus, a bit value of 1 will result in <strong>the</strong> accumulator only if a corresponding bit positionis set to a value of 1 in <strong>the</strong> accumulator or in <strong>the</strong> storage word, but not both.Processor Instructions 4-21

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