Analog Devices ADSP-BF53x Blackfin Reference page 596

Instruction Overview
• For a 32-bit input, Sign Bit returns the number of leading sign bits
minus one, which is in the range 0 through 31. An input of all
zeros or all ones returns +31 (all sign bits).
• For a 40-bit Accumulator input, Sign Bit returns the number of
leading sign bits minus 9, which is in the range –8 through +31. A
negative number is returned when the result in the Accumulator
has expanded into the extension bits; the corresponding normaliza-
tion will shift the result down to a 32-bit quantity (losing
precision). An input of all zeros or all ones returns +31.
The result of the
ment to
ASHIFT
the following formats (S == signbit, M == magnitude bit).
16-bit: S.MMM MMMM MMMM MMMM
32-bit: S.MMM MMMM MMMM MMMM MMMM MMMM MMMM MMMM
40-bit: SSSS SSSS S.MMM MMMM MMMM MMMM MMMM MMMM MMMM MMMM
In addition, the
form the new exponent.
The Sign Bit instruction does not implicitly modify the input value. For
32-bit and 16-bit input, the
same D-register. Doing this explicitly modifies the
Flags Affected
None
The ADSP-BF535 processor has fewer
operate differently than subsequent Blackfin family products. For
more information on the ADSP-BF535 status flags, see
on page
15-84 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
instruction can be used directly as the argu-
SIGNBITS
to normalize the number. Resultant numbers will be in
instruction result can be subtracted directly to
SIGNBITS
dest_reg
A-3.
and
sample_register
sample_register
flags and some flags
ASTAT
can be the
.
Table A-1