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.
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...