Multiply Accumulator (Multiplier)
2-24
ADSP-2126x SHARC Processor Hardware Reference
The multiplier transfers input operands during the first half of the proces-
sor cycle and transfers results during the second half of the cycle. With
this arrangement, the multiplier can read and write the same register file
location in a single cycle.
For fixed-point multiplies, the multiplier reads the inputs from the upper
32 bits of the data registers. Fixed-point operands may be either both in
integer format or both in fractional format. The format of the result
matches the format of the inputs. Each fixed-point operand may be either
an unsigned or a twos-complement number. If both inputs are fractional
and signed, the multiplier automatically shifts the result left one bit to
remove the redundant sign bit. The register name(s) within the multiplier
instruction specify input data type(s)—Fx for floating-point and Rx for
fixed-point.
Multiplier Result Register (Fixed-Point)
Fixed-point operations place 80-bit results in the multiplier’s foreground
MRF
register or background
MRB
register, depending on which is active. For
more information on selecting the result register, see
ary) Data Registers” on page 2-40
The location of a result in the
MRF
register’s 80-bit field depends on
whether the result is in fractional or integer format, as shown in
. If the result is sent directly to a data register, the 32-bit result
with the same format as the input data is transferred, using bits 63-32 for
a fractional result or bits 31-0 for an integer result. The eight LSBs of the
40-bit register file location are zero-filled.
Fractional results can be rounded-to-nearest before being sent to the regis-
ter file. If rounding is not specified, discarding bits 31-0 effectively
truncates a fractional result (rounds to zero). For more information on
rounding, see
Summary of Contents for ADSP-21261 SHARC
Page 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Page 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Page 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Page 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Page 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Page 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Page 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Page 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Page 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Page 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Page 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Page 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...