ADSP-BF535 Blackfin Processor Hardware Reference
14-3
USB Device
• Arbitration granted to the USB DMA channel within 3 to 5 USB
cycles (with
SCLK
=100 MHz) after the assertion of its request from
a host
If the arbitration requirement is not met, then USB Bulk, Interrupt, and
Control In packet transfers may be terminated prematurely, resulting in
degraded USB performance. Potentially, this can add complexity to the
USB driver code. To minimize degraded USB performance, a system clock
(
SCLK
) minimum of 100 MHz is recommended, but the
ADSP-BF535
Blackfin Embedded Processor Data Sheet
should be consulted.
Because SPORTs have a higher arbitration priority than the USB
on the DAB bus, USB data transfers may be affected when there is
excessive SPORT activity coupled with USB transactions on the
DAB bus. This condition could also occur on an external memory
access using MemDMA to a high latency external memory.
USB Requirements
The references listed at the end of this chapter describe the USB protocol
in detail. This section gives a brief description of some features of the pro-
tocol used for this particular USB device implementation.
Master and Slave Buses
The USB is a master-slave bus, in which a single master generates data
transfer requests to the attached slaves, and allocates bandwidth on the
serial cable according to a specific algorithm.
The bus master is referred to as the USB host, and the bus slaves are
referred to as USB devices. Each USB device implements one or more
USB endpoints, which are similar to virtual data channels. Each endpoint
on a USB device operates independently of all the others.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...