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

Add Immediate (PAI)0 5 8 15Op code0 1 1 1 0III 1R DisplacementX X X1 1 1 1 1 1 1 17 0-7 X XThe contents of the displacement field in the instruction are added algebraically tothe contents of the register specified by R. An R field of 000 specifies the accumulator.Before the addition takes place, the 8-bit displacement field is expanded to 16 bitsby propagating the displacement sign-bit (bit 8) value through the high-order bits(that is, bits 0 to 7 take on the value of the sign bit). The resulting sum replacesthe contents of the index register or accumulator. The instruction word is not changed.The carry and result indicators are set to reflect the result in the index registeror accumulator.The overflow indicator is set to reflect the result only if it has not been set bya previous operation. If the overflow indicator was previously set on, it will not bechanged by the result of an add immediate instruction. If an overflow occurs, theaccumulator will contain the correct low-order 16 bits of the result and the carryindicator will be turned on if the result is negative.Example:PAI instruction(R=000 specifiesdisplacement is addedto accumulator)0 5 8 15Op code0 1 1 1 0R0 0 0I IDisplacement0 0 1 1 (1 1 1 17 0 3 FContents of accumulator 0011 1111 0000 0000Expanded displacement +0000 0000 0011 1111Result in accumulator 0011 1111 0011 1111Subtract (PS)0 5 8 15Op code R Displacement1 0 0 1 0 X X XIII! 1 I 1 1 1 1 1 1 19 0-7 X XThe contents of the storage location specified by the effective address are subtractedalgebraically from the contents of the accumulator. The resulting difference replacesthe contents of the accumulator; the contents of the addressed storage location arenot changed.If R=000, the effective address of the data in storage is formed by using the IARas the base register. If the R field is nonzero (R =001 to 111), the effective addressis formed using an index register as the base register.Processor Instructions 4-15