LSH32

Features:

32-bit Input, 32-bit Output Multiplexed to 16 Lines
Full 0-31 Position Barrel Shift Capability
Integral Priority Encoder for 32-bit Floating Point Normalization
Sign-Magnitude or Two's Complement Mantissa Representation
32-bit Linear Shifts with Sign or Zero Fill
Independent Priority Encoder Outputs for Block Floating Point
68-pin PLCC, J-Lead


Pinout




Specifications

Storage temperature .............................65°C to +150°C Operating ambient temperature ........................................................ 55°C to +125°C VCC supply voltage with respect to ground ............................................. 0.5 V to +7.0 V Input signal with respect to ground .................................... 3.0 V to +7.0 V Signal applied to high impedance output ................................................................ 3.0 V to +7.0 V Output current into low outputs ....................................................... 25 mA Latchup current .......................................................................... > 400 mA


Description

The LSH32 is a 32-bit high speed shifter designed for use in floating point normalization, word pack/ unpack, field extraction, and similar applications. It has 32 data inputs, and 16 output lines. Any shift configuration of the 32 inputs, including circular (barrel) shifting, left shifts with zero fill, and right shift with sign extend are possible. In addition, a built-in priority encoder is provided to aid floating point normalization.

configured such that any contiguous 16-bit field (including wraparound of the 32 inputs) may be presented to the output pins under control of the shift code field (wrap mode). Alternatively, the wrap feature may be disabled, resulting in zero or sign bit fill, as appropriate (fill mode). The shift code control assignments and the resulting input to output mapping for the wrap mode are shown in Table 1.

Essentially the LSH32 is configured as a left shift device. That is, a shift code of 000002 results in no shift of the input field. A code of 000012 provides an effective left shift of 1 position, etc. When viewed as a right shift, the shift code corresponds to the two's complement of the shift distance, i.e., a shift code of 111112 (110) results in a right shift of one position, etc.

When not in the wrap mode, the LSH32 fills bit positions for which there is no corresponding input bit. The fill value and the positions filled depend on the RIGHT/LEFT (R/L) direction pin. This pin is a don't care input when in wrap mode. For left shifts in fill mode, lower bits are filled with zero as shown in Table 2. For right shifts, however, the SIGN input is used as the fill value. Table 3 depicts the bits to be filled as a function of shift code for the right shift case. Note that the R/L input changes only the fill convention, and does not affect the definition of the shift code. In fill mode, as in wrap mode, the shift code input represents the number of shift positions directly for left shifts, but the two's complement of the shift code results in the equivalent right shift

. However, for fill mode the R/L input can be viewed as the most The LSH32 is a 32-bit high speed shifter designed for use in floating point normalization, word pack/ unpack, field extraction, and similar applications. It has 32 data inputs, and 16 output lines. Any shift configuration of the 32 inputs, including circular (barrel) shifting, left shifts with zero fill, and right shift with sign extend are possible. In addition, a built-in priority encoder is provided to aid floating point normalization. SHIFT ARRAY The 32 inputs to the LSH32 are applied to a 32-bit shift array. The 32 outputs of this array are multiplexed down to 16 lines for presentation at the device outputs. The array may be 16 OE MS/LS 32-bit BARREL SHIFT ARRAY 16 16 2:1 32 SIGN I31-I0 Y15-Y0