Signbits - Analog Devices ADSP-BF53x Blackfin Reference

SIGNBITS

General Form
dest_reg = SIGNBITS sample_register
Syntax
Dreg_lo = SIGNBITS Dreg ;
Dreg_lo = SIGNBITS Dreg_lo_hi ;
Dreg_lo = SIGNBITS A0 ;
Dreg_lo = SIGNBITS A1 ;
Syntax Terminology
:
Dreg R7–0
:
Dreg_lo R7–0.L
:
Dreg_lo_hi R7–0.L
Instruction Length
In the syntax, comment (b) identifies 32-bit instruction length.
Functional Description
The Sign Bit instruction returns the number of sign bits in a number, and
can be used in conjunction with a shift to normalize numbers. This
instruction can operate on 16-bit, 32-bit, or 40-bit input numbers.
• For a 16-bit input, Sign Bit returns the number of leading sign bits
minus one, which is in the range 0 through 15. There are no spe-
cial cases. An input of all zeros returns +15 (all sign bits), and an
input of all ones also returns +15.
ADSP-BF53x/BF56x Blackfin Processor Programming Reference
/* 32-bit sample (b) */
/* 40-bit sample (b) */
/* 40-bit sample (b) */
,
R7–0.H
Arithmetic Operations
/* 16-bit sample (b) */
15-83