Lucent Technologies DSP1611, Information Manual

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DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR Information Manual
Bit Manipulation Unit April 1998
13-2
DRAFT COPY
Lucent Technologies Inc.
13.2 Software View
13.2.1 Instruction Set
The following are the instructions for the BMU. Instruction set details are found in Section 4.5.7, BMU Instructions .
BMU
aD = aT SHIFT aS
aD = aS SHIFT arM
aD = aS SHIFT IM16
aD = exp (aS)
aD = norm (aS, arM)
aD = extracts (aS, arM)
aS = extractz (aS, arM)
aD = extracts (aS, IM16)
aD = extractz (aS, IM16)
aD = insert (aS, arM)
aD = insert (aS, IM16)
aD = aS : aaT
13.2.2 Shifting Operations
In all of the shifting operations, the source accumulator and the destination accumulator can be the same or
different. If the source and destination accumulators are different, the source remains the same after the shift. The
amount of shift is defined by a value in one of the ar registers, in the high half of an accumulator, or from an imme-
diate data word. The amount of shift is a signed value. If a negative shift is called for, the direction of shift is auto-
matically reversed. The following describes the four types of shifts.
In the logical right shift (>>> ) bits 31—0 of the source accumulator are shifted to the right into the destination
accumulator. The open upper bits after the shift are filled in with zeros.
5-4213
Figure 13-2. Logical Right Shift
35 32 31 16 15 0
0----------------0
BEFORE
AFTER
LOGICAL RIGHT
SHIFT