ADSP-BF53x/BF56x Blackfin Processor Programming Reference
2-15
Computational Units
unsigned, a mixture, or a rounding operation). The 32-bit result from the
multipliers is assumed to be signed; it is sign-extended across the full
40-bit width of the
A0
or
A1
registers.
The processor supports two modes of format adjustment: the fractional
mode for fractional operands (1.15 format with 1 sign bit and 15 frac-
tional bits) and the integer mode for integer operands (16.0 format).
When the processor multiplies two 1.15 operands, the result is a 2.30
(2 sign bits and 30 fractional bits) number. In the fractional mode, the
multiplier automatically shifts the multiplier product left one bit before
transferring the result to the multiplier result register (
A0
,
A1
). This shift of
the redundant sign bit causes the multiplier result to be in 1.31 format,
which can be rounded to 1.15 format. The resulting format appears in
Figure 2-5 on page 2-18
.
In the integer mode, the left shift does not occur. For example, if the oper-
ands are in the 16.0 format, the 32-bit multiplier result would be in 32.0
format. A left shift is not needed and would change the numerical
representation. This result format appears in
Figure 2-6 on page 2-19
.
Multiplier results generate status information when they update accumu-
lators or when they are transferred to a destination register in the register
file. For more information, see
“Multiplier Instruction Summary” on page
2-38
.
Shifter Data Types
Many operations in the shifter are explicitly geared to signed (two’s-com-
plement) or unsigned values—logical shifts assume unsigned magnitude
or binary string values, and arithmetic shifts assume two’s-complement
values.
The exponent logic assumes two’s-complement numbers. The exponent
logic supports block floating point, which is also based on two’s-comple-
ment fractions.
Содержание ADSP-BF53x Blackfin
Страница 38: ...Conventions xxxviii ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 134: ...System Reset and Powerup 3 18 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 324: ...Instruction Overview 7 20 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 486: ...Instruction Overview 13 28 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 512: ...Instruction Overview 14 26 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 604: ...Instruction Overview 15 92 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 688: ...Instruction Overview 18 48 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 742: ...Instruction Overview 19 54 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 752: ...Examples 20 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 780: ...Product Identification Register 21 28 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 790: ...ADSP BF535 Flags A 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 800: ...Performance Monitor Registers B 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 994: ...Instructions Listed By Operation Code C 194 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 1042: ...Index I 40 ADSP BF53x BF56x Blackfin Processor Programming Reference...