Data Types
2-14
ADSP-BF53x/BF56x Blackfin Processor Programming Reference
ALU Data Types
Operations on each ALU treat operands and results as either 16- or 32-bit
binary strings, except the signed division primitive (
DIVS
). ALU result sta-
tus bits treat the results as signed, indicating status with the overflow flags
(
AV0
,
AV1
) and the negative flag (
AN
). Each ALU has its own sticky over-
flow flag,
AV0S
and
AV1S
. Once set, these bits remain set until cleared by
writing directly to the
ASTAT
register. An additional
V
flag is set or cleared
depending on the transfer of the result from both accumulators to the reg-
ister file. Furthermore, the sticky
VS
bit is set with the
V
bit and remains
set until cleared.
The logic of the overflow bits (
V
,
VS
,
AV0
,
AV0S
,
AV1
,
AV1S
) is based on
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
AVn
, the corresponding overflow flags. Add-
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 (
AC0
,
AC1
) is based on unsigned magnitude
arithmetic. The bit is set if a carry is generated from bit 16 (the MSB).
The carry bits (
AC0
,
AC1
) are most useful for the lower word portions of a
multiword operation.
ALU results generate status information. For more information about
using ALU status, see
“ALU Instruction Summary” on page 2-30
.
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
Summary of Contents for ADSP-BF53x Blackfin
Page 38: ...Conventions xxxviii ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 134: ...System Reset and Powerup 3 18 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 324: ...Instruction Overview 7 20 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 486: ...Instruction Overview 13 28 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 512: ...Instruction Overview 14 26 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 604: ...Instruction Overview 15 92 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 688: ...Instruction Overview 18 48 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 742: ...Instruction Overview 19 54 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 752: ...Examples 20 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 790: ...ADSP BF535 Flags A 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 800: ...Performance Monitor Registers B 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Page 1042: ...Index I 40 ADSP BF53x BF56x Blackfin Processor Programming Reference...