Alu Data Types; Multiplier Data Types - Analog Devices ADSP-BF53x Blackfin Reference

Data Types

ALU Data Types

Operations on each ALU treat operands and results as either 16- or 32-bit
binary strings, except the signed division primitive (
tus bits treat the results as signed, indicating status with the overflow flags
( , ) and the negative flag (
AV0 AV1
flow flag,
AV0S
writing directly to the
depending on the transfer of the result from both accumulators to the reg-
ister file. Furthermore, the sticky
set until cleared.
The logic of the overflow bits (
two's-complement arithmetic. A bit or set of bits is set if the Most Signifi-
cant Bit (MSB) changes in a manner not predicted by the signs of the
operands and the nature of the operation. For example, adding two posi-
tive numbers must generate a positive result; a change in the sign bit
signifies an overflow and sets
ing a negative and a positive number may result in either a negative or
positive result, but cannot cause an overflow.
The logic of the carry bits (
arithmetic. The bit is set if a carry is generated from bit 16 (the MSB).
The carry bits (
multiword operation.
ALU results generate status information. For more information about
using ALU status, see

Multiplier Data Types

Each multiplier produces results that are binary strings. The inputs are
interpreted according to the information given in the instruction itself
(whether it is signed multiplied by signed, unsigned multiplied by
2-14 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
AN
and . Once set, these bits remain set until cleared by
AV1S
register. An additional
ASTAT
,
V
, the corresponding overflow flags. Add-
AVn
,
AC0 AC1
, ) are most useful for the lower word portions of a
AC0 AC1
"ALU Instruction Summary" on page
). Each ALU has its own sticky over-
bit is set with the
VS
, , ,
VS AV0 AV0S AV1
) is based on unsigned magnitude
). ALU result sta-
DIVS
flag is set or cleared
V
bit and remains
V
, ) is based on
AV1S
2-30.