CPU16
REFERENCE MANUAL
DIGITAL SIGNAL PROCESSING
MOTOROLA
11-9
11.7.3.5 ACE — Add E to AM
ACE is used with either of the FMULS or MAC instructions. It allows direct addition of
16-bit signed fractions to accumulator M. The content of accumulator E is added to
AM[31:16]. Bits 15 to 0 of accumulator M are not affected.
The value in E is assumed to be a 16-bit signed fraction with an implied radix point
between bits 15 and 14.
EV and MV in the CCR are set according to the result of ACE operation.
11.7.4 Bit Manipulation Instructions
There are three instructions that operate directly on the bits in accumulator M. ASLM
and ASRM perform 36-bit arithmetic shifts and CLRM clears the accumulator.
11.7.4.1 ASLM — Arithmetic Shift Left AM
Shifts all 36 bits of accumulator M one place to the left. Bit 35 is transferred to the CCR
C bit. Bit 0 is loaded with a zero.
EV, MV, and N in the CCR are set according to the result of ASLM operation.
11.7.4.2 ASRM — Arithmetic Shift Right AM
Shifts all 36 bits of accumulator M one place to the right. Bit 0 is transferred to the CCR
C bit. Bit 35 is held constant.
EV, MV, and N in the CCR are set according to the result of ASRM operation.
11.7.4.3 CLRM — Clear AM
CLRM provides a simple way to initialize accumulator M when a starting value of
$000000000 is needed. AM[35:0] are cleared to zero. EV and MV in the CCR are also
cleared.
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