Multiply Accumulators (Multipliers)
2-34
ADSP-BF535 Blackfin Processor Hardware Reference
Placing Multiplier Results in Multiplier Accumulator Registers
As shown in
Figure 2-10 on page 2-29
, each multiplier has a dedicated
accumulator,
A0
or
A1
. Each accumulator register is divided into three sec-
tions:
A0.L/A1.L
(bits 15:0),
A0.H/A1.H
(bits 31:16), and
A0.X/A1.X
(bits
39:32).
When the multiplier writes to its result accumulator registers, the 32-bit
result is deposited into the lower bits of the combined accumulator regis-
ter, and the MSB is sign extended into the upper eight bits of the register
(
A0.X/A1.X
).
Multiplier output can be deposited not only in the
A0
or
A1
registers, but
also in a variety of 16- or 32-bit Data registers in the Data Register File.
Rounding or Saturating Multiplier Results
On a multiply and accumulate operation, the accumulator data can be sat-
urated and, optionally, rounded for extraction to a register or register half.
When a multiply deposits a result only in a register or register half, the sat-
uration and rounding works the same way.
The rounding and saturation operations work as follows:
• Rounding is applied only to fractional results except for the
IH
option, which applies rounding and high half extraction to an inte-
ger result.
• The rounded result is obtained by adding 0x8000 to the accumula-
tor (for MAC) or multiply result (for mult) and then saturating to
32-bits.
For more information, see “Rounding Multiplier Results”
on page 2-18.
• If an overflow or underflow has occurred, the saturate operation
sets the specified result register to the maximum positive or nega-
tive value. For more information, see the following section.
Содержание ADSP-BF535 Blackfin
Страница 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Страница 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 908: ...SDRAM Controller External Bus Interface Unit B 36 ADSP BF535 Blackfin Processor Hardware Reference...