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12-34 Intel® PXA255 Processor Developer’s Manual
USB Device Controller
12.6.7.4 DMA Enable (DME)
The DMA enable is used by the UDC to control the timing of the data received interrupt. If the bit
is set, the interrupt is asserted when the end of packet is received and the receive FIFO has less than
32 bytes of data in it. If the bit is not set, the interrupt is asserted when the end of packet is received
and all of the received data is still in the receive FIFO.
12.6.7.5 Bits 5:4 Reserved
Bits 5:4 are reserved for future use.
12.6.7.6 Receive FIFO Not Empty (RNE)
The receive FIFO not empty bit indicates that the receive FIFO has unread data in it. When the
UDCCSx[RPC] bit is set, this bit must be read to determine if there is any data in the FIFO that
DMA did not read. The receive FIFO must continue to be read until this bit clears or data will be
lost.
12.6.7.7 Receive Short Packet (RSP)
The receive short packet bit is used by the UDC to indicate that the received OUT packet in the
active buffer currently being read is a short packet or zero-sized packet. This bit is updated by the
UDC after the last byte is read from the active buffer and reflects the status of the new active
buffer. If UDCCSx[RSP] is a one and UDCCSx[RNE] is a zero, it indicates a zero-length packet. If
a zero-length packet is present, the core must not read the data register. UDCCSx[RSP] clears
when the next OUT packet is received.
These are read/write registers. Ignore reads from reserved bits. Write zeros to reserved bits.
12.6.8 UDC Endpoint x Control/Status Register (UDCCS5/10/15)
UDCCS5/10/15, shown in Table 12-19 contains 6 bits that are used to operate endpoint(x), an
Interrupt IN endpoint.
Table 12-19. UDCCS5/10/15 Bit Definitions (Sheet 1 of 2)
0x 4060_0024
0x 4060_0038
0x 4060_004C
UDCCS5
UDCCS5
UDCCS15
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
FST
SST
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
Bits Name Description
31:8 — reserved
7TSP
Transmit short packet (read/write 1 to set).
1 = Short packet ready for transmission.
6 — reserved