ADSP-BF535 Blackfin Processor Hardware Reference
7-13
Chip Bus Hierarchy
The PCI controller, the core processor, and the DAB must arbi-
trate for access to external memory through the EBIU. This
additional arbitration latency added to the latency required to read
off-chip memory devices can significantly degrade DAB through-
put, potentially causing peripheral data buffers to underflow or
overflow. If you use DMA peripherals other than the Memory
DMA controller, and you target external memory for DMA
accesses, you need to carefully analyze your specific traffic patterns
to ensure that those isochronous peripherals targeting internal
memory have enough allocated bandwidth and the appropriate
maximum arbitration latencies.
When two or more DMA master channels are actively requesting the
DAB, bus utilization is considerably higher due to the DAB’s pipelined
design. Bus arbitration cycles are concurrent with the previous DMA
access’s data cycles.
Memory DMA transfers typically result in repeated accesses to the same
memory location. Because the memory DMA controller has the potential
of simultaneously accessing on-chip and off-chip memory, considerable
throughput can be achieved. The throughput rate for an on-chip/off-chip
memory access is limited by the slower of the two accesses. An additional
1 to 2 cycles per burst access is inherent in the design.
Burst Read from External Mem-
ory (SDRAM)
(16-byte and 32-byte)
All ratios
9-1-1-1
9-1-1-1-1-1-1-1
Write to SDRAM (burst of 8)
All ratios
4-2-2-2
4-2-2-2-2-2-2-2
Burst Read from Async Memory All ratios
12-4-4-4
12-4-4-4-4-4-4-4
Burst Write to Async Memory
All ratios
12-4-4-4
12-4-4-4-4-4-4-4
Table 7-3. DAB Latencies (Cont’d)
Use of DAB
Core Clock to System
Clock Ratio
(CCLK/SCLK)
Latency in SCLKs
Burst of 4
Latency in SCLKs
Burst of 8
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...