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

Shift Left Circular (PSLC)0 5 8 11 15Op code0 0 0 1I I10IXRX XIMod0 0 0I ICountXXXXX0-7 0 or 1 XAll 16 bits in the index register (R), or the accumulator if R=000, are rotated left bythe number of bits specified in the count field. This means that bits shifted out of thehigh-order position (bit 0) reenter at the low-order position (bit 15). Therefore, nobits are lost; they are just rearranged.The shift count field can specify any decimal value from 0 to 16. Shift counts greaterthan 16 are invalid and cause a program check interruption. A shift count of 0 is validand serves a useful purpose. Although no rotating takes place, this is a simple methodof setting the result indicators to reflect the current contents of the R register. Ashift count of 16 has the same effect because the bits are rotated until they return totheir original positions.The carry and overflow indicators are not changed. The result indicators are changedto reflect the final contents of the R register.Example:Assume a left circular shift of four bits in index register 40 5 8 15PSLC instructionOp code R Mod Count0 0 0 1 0 1 0 0 0 0 0 010 1 0 0III! It 11 III!1 4 0 4Original valueAfter first shiftAfter second shift• •• •• •After fourth shift0000 0000 0000 111 1