Analog Devices ADSP-BF53x Blackfin Reference page 533

Both instruction versions align the dividend for the next iteration by left
shifting the dividend one bit to the left (without carry). This left shift
accomplishes the same function as aligning the divisor one bit to the right,
such as one would do in manual binary division.
The format of the quotient for any numeric representation can be deter-
mined by the format of the dividend and divisor. Let:
• NL represent the number of bits to the left of the binal point of the
dividend, and
• NR represent the number of bits to the right of the binal point of
the dividend (numerator);
• DL represent the number of bits to the left of the binal point of the
divisor, and
• DR represent the number of bits to the right of the binal point of
the divisor (denominator).
Then the quotient has NL – DL + 1 bits to the left of the binal point and
NR – DR – 1 bits to the right of the binal point. See the following
example.
Dividend (numerator)
Divisor (denominator)
Quotient
Some format manipulation may be necessary to guarantee the validity of
the quotient. For example, if both operands are signed and fully fractional
(dividend in 1.31 format and divisor in 1.15 format), the result is fully
ADSP-BF53x/BF56x Blackfin Processor Programming Reference
BBBB B . BBB BBBB BBBB BBBB BBBB BBBB BBBB
NL bits NR bits
BB . BB BBBB BBBB BBBB
DL bits DR bits
BBBB . BBBB BBBB BBBB
NL - DL +1 NR - DR - 1
(5 - 2 + 1) (27 - 14 - 1)
4.12 format
Arithmetic Operations
15-21