Shifter Operation - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

• Bit field manipulation operations, including extract and deposit
• Fixed-point/floating-point conversion operations, including expo-
nent extract, number of leading 1s or 0s

Shifter Operation

The shifter takes from one to three inputs: X input, Y input, and Z input.
The inputs (also known as operands) can be any register in the register
file. Within a shifter instruction, the inputs serve as follows.
• The X input provides data that is operated on.
• The Y input specifies shift magnitudes, bit field lengths, or bit
positions.
• The Z input provides data that is operated on and updated.
In the following example,
Z input. The shifter returns one output (
Rn = Rn OR LSHIFT Rx BY Ry;
As shown in Figure
32 bits of a register file location (bits 39-8) or from an immediate value in
the instruction. The shifter transfers operands during the first half of the
cycle and transfers the result to the upper 32 bits of a register (with the
eight LSBs zero-filled) during the second half of the cycle. With this
arrangement, the shifter can read and write the same register file location
in a single cycle.
The X input and Z input are always 32-bit fixed-point values. The Y input
is a 32-bit fixed-point value or an 8-bit field (shf8), positioned in the reg-
ister file. These inputs appear in
ADSP-2126x SHARC Processor Hardware Reference
is the X input,
Rx
2-9, the shifter fetches input operands from the upper
Figure
Processing Elements
is the Y input, and
Ry
) to the register file.
Rn
2-9.
is the
Rn
2-31