Multiply Accumulator (Multiplier); Multiplier Operation - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

Multiply Accumulator (Multiplier)

The multiplier performs fixed-point or floating-point multiplication and
fixed-point multiply/accumulate operations. Fixed-point multiply/accu-
mulates are available with either cumulative addition or cumulative
subtraction. Multiplier floating-point instructions operate on 32-bit or
40-bit floating-point operands and output 32-bit or 40-bit floating-point
results. Multiplier fixed-point instructions operate on 32-bit fixed-point
data and produce 80-bit results. Inputs are treated as fractional or integer,
unsigned or twos-complement. Multiplier instructions include:
• Floating-point multiplication
• Fixed-point multiplication
• Fixed-point multiply/accumulate with addition, rounding optional
• Fixed-point multiply/accumulate with subtraction, rounding
optional
• Rounding result register
• Saturating result register
• Clearing result register

Multiplier Operation

The multiplier takes two inputs: X input and Y input. These inputs (also
known as operands) can be any data registers in the register file. The
multiplier can accumulate fixed-point results in the local Multiplier Result
( ) registers or write results back to the register file. The results in
MRF
can also be rounded or saturated in separate operations. Floating-point
multiplies yield floating-point results, which the multiplier always writes
directly to the register file.
ADSP-2126x SHARC Processor Hardware Reference
Processing Elements
MRF
2-23