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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262--, Revision: 004US
321
USB 1.1 Device Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network
Processors
8.5.14.8
Receive Short Packet (RSP)
The UDC uses the receive short packet bit 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 UDCCS12[RSP] is a 1 and UDCCS12[RNE] is a 0, it indicates a zero-length packet. If
a zero-length packet is present, the Intel XScale processor must not read the data
register. UDCCS12[RSP] is cleared when the next OUT packet is received.
8.5.15
UDC Endpoint 13 Control/Status Register
(UDCCS13)
The UDC Endpoint 13 Control Status Register contains four bits that are used to
operate Endpoint 13, an Isochronous IN endpoint.
Register Name:
UDCCS12
Hex Offset Address:
0 x C800 B040
Reset Hex Value:
0 x 00000000
Register
Description:
Universal Serial Bus Device Controller Endpoint 12 Control and Status Register
Access: Read/Write
Bits
31
8
7
6
5
4
3
2
1
0
(Reserved)
RSP
RNE
FST
SS
T
(Rsvd
)
(Rsvd
)
RPC
RFS
X
0
0
0
0
0
0
0
0
Resets (Above)
Register
UDCCS12
Bits
Name
Description
31:8
Reserved for future use.
7
RSP
Receive short packet (read only).
1 = Short packet received and ready for reading.
6
RNE
Receive FIFO not empty (read-only).
0 = Receive FIFO empty.
1 = Receive FIFO not empty.
5
FST
Force stall (read/write).
1 = Issue STALL handshakes to OUT tokens.
4
SST
Sent stall (read/write 1 to clear).
1 = STALL handshake was sent.
3
(Reserved)
2
(Reserved). Always reads zero.
1
RPC
Receive packet complete (read/write 1 to clear).
0 = Error/status bits invalid.
1 = Receive packet has been received and error/status bits are valid.
0
RFS
Receive FIFO service (read-only).
0 = Receive FIFO has less than 1 data packet.
1 = Receive FIFO has 1 or more data packets.