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SYNTAX      [<LABEL>] SPAC

OPERANDS    None

EXECUTION   (PC) + 1 . PC
            (ACC) - (shifted P register) . ACC
            Affects OV; affected by PM and OVM.
            Affects C (TMS320C25).
            Not affected by SXM.

DESCRIPTION The contents of the P register, shifted as defined by the PM
            status bits, are subtracted from the contents of the
            accumulator. The result is stored in the accumulator. Note
            that SPAC is unaffected by SXM; the P register is always sign-
            extended.

            The SPAC instruction is a subset of LTS, MPYS, and SQRS.

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  1  0  1  1  0 |
            +-----------------------------------------------+

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   |   n   |   n   |  n+p  |  n+p   |   -   |   -   |
            |-------+-------+-------+--------+-------+-------|
     'C25   |   n   |   n   |  n+p  |  n+p   |   n   |   n   |
            +------------------------------------------------+



EXAMPLE     SPAC              (PM = 0)

               BEFORE             AFTER

                P >24             P >24
            ACC X >3C         ACC 1 >18
                C                 C
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