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SYNTAX      [<LABEL>] SPM <constant>

OPERANDS    0 . constant . 3

EXECUTION   (PC) + 1 . PC
            Constant . product register shift mode (PM) status bits
            Affects PM.

DESCRIPTION The two low-order bits of the instruction word are copied into
            the PM field of status register ST1. The PM status bits
            control the P register output shifter. This shifter has the
            ability to shift the P register output either one or four bits
            to the left or six bits to the right, or to perform no shift.
            The bit combinations and their meanings are:

                  PM                      ACTION

                  00          No shift of multiplier output
                  01          Output left-shifted 1 place and zero-filled
                  10          Output left-shifted 4 places and zero-filled
                  11          Output right-shifted 6 places, sign-
                              extended; LSB bits lost.

WORDS       1

ENCODING    15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
            +-----------------------------------------------+
            |1  1  0  0  1  1  1  0  0  0  0  0  1  0|  PM  |
            +-----------------------------------------------+

CYCLES

            +------------------------------------------------+
            |     Cycle Timings for a Single Instruction     |
            |------------------------------------------------|
            | PI/DI | PI/DE | PE/DI | PE/DE  | PR/DI | PR/DE |
            |-------+-------+-------+--------+-------+-------|
      '20   |   1   |   1   |  1+p  |  1+p   |   -   |   -   |
            |-------+-------+-------+--------+-------+-------|
     'C25   |   1   |   1   |  1+p  |  1+p   |   1   |   1   |
            |------------------------------------------------|
            |     Cycle Timings for a Repeat Instruction     |
            |------------------------------------------------|
      '20   |       not repeatable           |   -   |   -   |
            |------------------------------------------------|
     'C25   |                 not repeatable                 |
            +------------------------------------------------+



EXAMPLE     SPM   3           Product register shift mode 3 is selected,
                              causing all subsequent transfers from the
                              product register to the ALU to be shifted
                              to the right six places.