LSH32 データシートの表示（PDF） - LOGIC Devices Incorporated
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LSH32 Datasheet PDF : 9 Pages
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DEVICES INCORPORATED
LSH32
32-bit Cascadable Barrel Shifter
TABLE 3. FILL MODE SHIFT CODE DEFINITIONS — RIGHT SHIFT
Shift Code Y31 Y30 Y29 ••• Y16 Y15 ••• Y2 Y1 Y0
00000
00001
00010
00011
•
•
•
01111
10000
10001
10010
•
•
•
11100
11101
11110
11111
S S S ••• S S ••• S S S
S S S ••• S S ••• S S I31
S S S ••• S S ••• S I31 I30
S S S ••• S S ••• I31 I30 I29
•
•
• ••• •
• ••• •
•
•
•
•
• ••• •
• ••• •
•
•
•
•
• ••• •
• ••• •
•
•
S S S ••• S S ••• I19 I18 I17
S
S
S ••• S I31 ••• I18 I17 I16
S
S
S ••• I31 I30 ••• I17 I16 I15
S
S
S ••• I30 I29 ••• I16 I15 I14
•
•
• ••• •
• ••• •
•
•
•
•
• ••• •
• ••• •
•
•
•
•
• ••• •
• ••• •
•
•
S
S
S ••• I20 I19 ••• I6
I5
I4
S
S
S ••• I19 I18 ••• I5
I4
I3
S
S I31 ••• I18 I17 ••• I4
I3
I2
S I31 I30 ••• I17 I16 ••• I3 I2 I1
TABLE 4. PRIORITY ENCODER FUNCTION TABLE
I31 I30 I29 ••• I16 I15 ••• I2 I1
1 X X ••• X X ••• X X
0 1 X ••• X X ••• X X
0 0 1 ••• X X ••• X X
•
•
• ••• •
• ••• •
•
•
•
• ••• •
• ••• •
•
0 0 0 ••• 1 X ••• X X
0 0 0 ••• 0 1 ••• X X
0 0 0 ••• 0 0 ••• X X
•
•
• ••• •
• ••• •
•
•
•
• ••• •
• ••• •
•
0 0 0 ••• 0 0 ••• 0 1
0 0 0 ••• 0 0 ••• 0 0
0 0 0 ••• 0 0 ••• 0 0
I0 Shift Code
X 00000
X 00001
X 00010
•
•
•
•
X 01111
X 10000
X 10001
•
•
•
•
X 11110
1 11111
0 11111
NORMALIZE MULTIPLXER
The NORM input, when asserted
results in the priority encoder output
driving the internal shift code inputs
directly. It is exactly equivalent to
routing the SO4–SO0 outputs back to
the SI4–SI0 inputs. The NORM input
provides faster normalization of 32-bit
data by avoiding the delay associated
with routing the shift code off chip.
When using the NORM function, the
LSH32 should be placed in fill mode,
with the R/L input low.
APPLICATIONS EXAMPLES
Normalization of mantissas up to 32
bits can be accomplished directly by a
single LSH32. The NORM input is
asserted, and fill mode and left shift
are selected. The normalized mantissa
is then available at the device output
in two 16-bit segments, under the
control of the output data multiplexer
select, the MS/LS.
If it is desirable to avoid the necessity
of multiplexing output data in 16-bit
segments, two LSH32 devices can be
used in parallel. Both devices receive
the same input word, with the MS/LS
select line of one wired high, and the
other low. Each device will then
independently determine the shift
distance required for normalization,
and the full 32 bits of output data will
be available simultaneously.
Special Arithmetic Functions
3
08/16/2000–LDS.32-Q
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