USB Programming Model
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ADSP-BF535 Blackfin Processor Hardware Reference
data phase in the setup packet, but the data phase may terminate early.
Bulk and interrupt transfers, however, appear only as a continuous stream
of packets to the USB.
To delineate blocks of data, the USB requires that all packets be sent at
the maximum size for the endpoint, except for the last packet in a group.
For example, if the endpoint’s maximum packet size is 8 bytes, and a
63-byte transfer is being performed, the data source would send 7 packets
at 8 bytes, and one last packet at 7 bytes. The software on the USB host or
the USB device recognizes the shortened data packet as the end of a group
of packets. If the data transfer ends on a packet boundary (that is, a
64-byte transfer, 8-byte packet size), the data source sends a last 0-byte
packet on the USB.
How to Transfer Data
Preparing a USB endpoint to transfer data consists of several steps:
1. For the first memory block, program the buffer offset and length
into the
USBD_EPADRx
and
USBD_EPLENx
registers. The offset address
is a word-aligned address in the ADSP-BF535 processor’s L2
memory.
2. Unmask the
USBD_BCSTAT
,
USBD_PC
, and
USBD_TC
interrupts.
3. Program the
USB_EPCFGx
register with these fields:
• Set the
USBD_MAX
field to the code for the endpoint’s maxi-
mum packet size.
• Set
USBD_TYP
to the code for the endpoint type.
• Set
USBD_DIR
to IN or OUT.
• Set
USBD_ARM
to 1.
4. Wait for interrupts.
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...