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Intel® PXA255 Processor Developer’s Manual 12-31
USB Device Controller
These are read/write registers. Ignore reads from reserved bits. Write zeros to reserved bits.
12.6.6 UDC Endpoint x Control/Status Register (UDCCS3/8/13)
USCCS3/8/13, shown in Table 12-17, contains 4 bits that are used to operate endpoint(x), an
Isochronous IN endpoint.
12.6.6.1 Transmit FIFO Service (TFS)
The transmit FIFO service bit is be set if one or fewer data packets remain in the transmit FIFO.
UDCCSx[TFS] is cleared when two complete data packets are in the FIFO. A complete packet of
data is signified by loading 256 bytes or by setting UDCCSx[TSP].
12.6.6.2 Transmit Packet Complete (TPC)
The the UDC sets transmit packet complete bit when an entire packet is sent to the host. When this
bit is set, the IRx bit in the appropriate UDC status/interrupt register is set if transmit interrupts are
enabled. This bit can be used to validate the other status/error bits in the endpoint(x) control/status
register. The UDCCSx[TPC] bit gets cleared by writing a one to it. This clears the interrupt source
for the IRx bit in the appropriate UDC status/interrupt register, but the IRx bit must also be cleared.
Setting this bit does not prevent the UDC from transmitting the next buffer. The UDC issues NAK
handshakes to all IN tokens if this bit is set and neither buffer has been triggered by writing
64 bytes or setting UDCCSx[TSP].
Table 12-17. UDCCS3/8/13 Bit Definitions
0x4060_001C
0x4060_0030
0x4060_0044
UDCCS3
UDCCS8
UDCC13
USB Device Controller
Bit
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
reserved
TSP
reserved
TUR
FTF
TPC
TFS
Reset X X X X X X X X X X X X X X X X X X X X X X X X 0 0 0 0 0 0 0 1
Bit Name Description
31:8 — reserved
7TSP
Transmit short packet (read/write 1 to set).
1 = Short packet ready for transmission.
6:4 — reserved
3TUR
Transmit FIFO underrun (read/write 1 to clear)
1 = Transmit FIFO experienced an underrun.
2 FTF
Flush Tx FIFO (always read 0/ write a 1 to set)
1 = 1 – Flush Contents of TX FIFO
1TPC
Transmit packet complete (read/write 1 to clear).
0 = Error/status bits invalid.
1 = Transmit packet has been sent and error/status bits are valid.
0TFS
Transmit FIFO service (read-only).
0 = Transmit FIFO has no room for new data
1 = Transmit FIFO has room for at least 1 complete data packet