section 7 - Index of

MPYR Signed Multiply and Round MPYROperation:±S1 *S2+r -+ D (parallel move)±S1 *S2+r -+ D (parallel move)±(S1 *2- n )+r -+ D (no parallel move)Assembler Syntax:MPYR (±)S1,S2,D (parallel move)MPYR (±)S2,S1,D (parallel move)MPYR (±)S,#n,D (no parallel move)Description: Multiply the two signed 24-bit source operands S1 and S2 (or the signed24-bit source operand S by the positive 24-bit immediate operand 2- n ), round the resultusing convergent rounding, and store it in the specified 56-bit destination accumulator D.The "-" sign option is used to negate the product prior to rounding. The default signoption is "+". The contribution of the LS bits of the result is rounded into the upper portionof the destination accumulator (A1 or B1) by adding a constant to the LS bits of the lowerportion of the accumulator (AO or BO). The value of the constant added is determined bythe scaling mode bits SO and S1 in the status register. Once the rounding has been completed,the LS bits of the destination accumulator D (AO or BO) are loaded with zeros tomaintain an unbiased accumulator value which may be reused by the next instruction.The upper portion of the accumulator (A1 or B1) contains the rounded result which maybe read out to the data buses. Refer to the RND instruction for more complete informationon the convergent rounding process.Example 1:MPYR - YO,YO,B (R3)-N3;square and negate YO, update R3Before ExecutionYOI~ ________ $_65_4_32_1 __ ~After ExecutionYOI~ ________ $_6_54_32_1 __ ~BI~ ___ $_OO_:O_OO_OO_O_:OO_O_OO_O __ ~ BI~ ___ $_F_F:_AF_E_3E_D_:O_OO_OO_O __ ~Explanation of Example 1: Prior to execution, the 24-bit YO register contains the value$654321 (0.791111112), and the 56-bit B accumulator contains the value$00:000000:000000 (0.0). The execution of the MPYR -YO,YO,B instruction squares the24-bit signed value in the YO register, negates the resulting 48-bit product, rounds theresult into B1, and zeros BO (-YO*YO=-0.625856790961748 approximately=$FF:AFE3EC:B76B7E, which is rounded to the value $FF:AFE3ED:000000=-0.625856757164002=B).