Figure 4-5.Extraction - Lucent Technologies DSP1617 Information Manual

DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
Instruction Set
4.5 Instruction Set
4.5.7 BMU Instructions (continued)
Note that the arithmetic left shift << for the BMU is defined differently than the arithmetic left shift for the special
function instruction (see
extended from the new bit 31 to be compatible with DSP16A.
Normalization and Exponent Computation
aD = exp (aS)
aD = norm (aS, arM)
Bit Field Extraction and Insertion
aD = extracts (aS, arM)
aD = extractz (aS, arM)
aD = extracts (aS, IM16)
aD = extractz (aS, IM16)
4-32
(continued)
Table 4-10). In the case of the special function left shift, the guard bits (35—32) are sign-
The number of redundant sign bits present in the 36-bit value of aS is computed and
placed in aDh (bits 35—16). The low half of aD (bits 15—0) is cleared. This exponent
is generated with respect to bit 31 of aS. Flags are set based on the value written to
aD.
The exponent of aS is computed and placed in arM. The 36-bit value in aS is then
normalized based on this exponent and placed in aD. Flags are set based on the
value written to aD.
An arbitrary selected sequence of contiguous bits in the 36-bit aS register is placed in
the low-order bits of aD and either sign- or zero-extended. (Sign for extracts, zero for
extractz.) This bit field is defined by the 16-bit value in arM. The upper 8 bits of arM
hold the width of the field (in bits), and the lower 8 bits of arM hold the OFFSET from
bit 0 of aS (in bits). Flags are set based on the value written to aD.
An arbitrary selected sequence of contiguous bits in the 36-bit aS register is placed in
the low-order bits of aD and either sign- or zero-extended. This bit field is defined by
the 16-bit immediate value IM16. The upper 8 bits of IM16 hold the width of the field
(in bits), and the lower 8 bits of IM16 hold the OFFSET from bit 0 of aS (in bits). Flags
are set based on the value written to aD.
SOURCE
ACCUMULATOR
ZERO EXTENDED OR
DESTINATION
SIGN EXTENDED
ACCUMULATOR
Figure 4-5. Extraction
DRAFT COPY
WIDTH OFFSET
SPECIFIED IN
IMMEDIATE
OR arM
LSB
Information Manual
April 1998
5-4152
Lucent Technologies Inc.