USB Programming Model
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ADSP-BF535 Blackfin Processor Hardware Reference
3. Wait for interrupts.
• If
USBD_TC
interrupt and
USBD_PC
interrupt, then the packet
transfer was error free.
• If
USBD_TC
interrupt and not
USBD_PC
interrupt, then the
packet transfer had a problem of some kind. The specific
problem must be handled by the programmer. Software
must determine whether this is an error or merely a
warning.
4. Number of bytes received is equal to the buffer size minus the value
remaining in the
USBD_EPLENx
register when the
USBD_TC
interrupt
is received. Take the steps required to complete the transfer in soft-
ware, then go back to step 2 and update the registers accordingly.
Note that no error retries are performed.
Control Transfers
In general, Control endpoints (usually endpoint 0) operate like Bulk end-
points. However, Control endpoints are bidirectional and follow a special
protocol that allows the USB host to send commands to the USB device.
Control transfers consist of three phases: a setup phase, a data phase, and a
status phase.
During the setup phase, the USB host sends an 8-byte setup packet to the
USB device. The format and contents of the packet are defined in the
USB specification.
The setup packet specifies information such as the type of command
(standard request, vendor-specific, device-class-specific), the direction of
the data phase (if any), the size of the data phase (if any), and the specific
command code.
After receiving the command, the device can choose to reject the com-
mand by stalling the endpoint, or it can process the command and
proceed through the data and status phases.
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...