Analog Devices ADSP-BF53x Blackfin Reference page 574

Instruction Overview
Table 15-4. Multiply and Multiply-Accumulate to Half-Register
Options (Cont'd)
Option Description
(IS) Signed integer format. Multiply 16.0 * 16.0 formats to produce 32.0 results. No
shift correction.
Sign extend 32.0 result to 40.0 format before copying or accumulating to Accumu-
lator. Then, saturate Accumulator to maintain 40.0 precision; Accumulator result
is between minimum 0x80 0000 0000 and maximum 0x7F FFFF FFFF.
Extract the lower 16 bits of the Accumulator. Saturate for 16.0 precision and copy
to the destination register half. Result is between minimum -2
15
2 -1 (or, expressed in hex, between minimum 0x8000 and maximum 0x7FFF).
(IU) Unsigned integer format. Multiply 16.0 * 16.0 formats to produce 32.0 results.
No shift correction.
Zero extend 32.0 result to 40.0 format before copying or accumulating to Accu-
mulator. Then, saturate Accumulator to maintain 40.0 precision; Accumulator
result is between minimum 0x00 0000 0000 and maximum 0xFF FFFF FFFF.
Extract the lower 16 bits of the Accumulator. Saturate for 16.0 precision and copy
to the destination register half. Result is between minimum 0 and maximum 2
(or, expressed in hex, between minimum 0x0000 and maximum 0xFFFF).
(T) Signed fraction with truncation. Multiply 1.15 * 1.15 formats to produce 1.31
results after shift correction. The special case of 0x8000 * 0x8000 is saturated to
0x7FFF FFFF to fit the 1.31 result. (Same as the Default mode.)
Sign extend 1.31 result to 9.31 format before copying or accumulating to Accumu-
lator. Then, saturate Accumulator to maintain 9.31 precision; Accumulator result
is between minimum 0x80 0000 0000 and maximum 0x7F FFFF FFFF.
To extract to half-register, truncate Accumulator 9.31 format value at bit 16. (Per-
form no rounding.) Saturate the result to 1.15 precision and copy it to the destina-
tion register half. Result is between minimum -1 and maximum 1-2
expressed in hex, between minimum 0x8000 and maximum 0x7FFF).
15-62 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
15
and maximum
16
-1
-15
(or,