Intel IXP42X Personal Computer User Manual


 
Intel
®
IXP42X product line and IXC1100 control plane processors—Universal Serial Bus (USB)
v1.1 Device Controller
Intel
®
IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor
DM September 2006
528 Order Number: 252480-006US
18.5.29 UDC Byte Count Register 14 (UBCR14)
The Byte-Count Register maintains the remaining byte count in the active buffer of out
endpoint 14.
18.5.29.1 Endpoint 14 Byte Count (BC[7:0])
The byte count is updated after each byte is read. When software receives an interrupt
that indicates the endpoint has data, it can read the byte count register to determine
the number of bytes that remain to be read.
The number of bytes that remain in the input buffer is equal to the byte count +1.
18.5.30 UDC Endpoint 0 Data Register (UDDR0)
The UDC Endpoint 0 Data Register is an 16-entry by 8-bit bidirectional FIFO. When the
host transmits data to the UDC Endpoint 0, the Intel XScale
®
processor reads the UDC
Endpoint 0 Register to access the data.
When the UDC sends data to the host, the Intel XScale
®
processor writes the data to
be sent in the UDC Endpoint 0 Register. The Intel XScale
®
processor can only read and
write the FIFO at specific points in a control sequence.
The direction that the FIFO flows is controlled by the UDC. Normally, the UDC is in an
idle state, waiting for the host to send commands. When the host sends a command,
the UDC fills the FIFO with the command from the host and the Intel XScale
®
processor
reads the command from the FIFO when it arrives. The only time the Intel XScale
®
processor may write the endpoint 0 FIFO is after a valid command from the host is
received and it requires a transmission in response.
Register Name: UBCR14
Hex Offset Address: 0 x C800B07C Reset Hex Value: 0x00000000
Register
Description:
Universal Serial Bus Device Endpoint 14 Byte Count
Access: Read-Only
Bits
31 87 0
(Reserved) BC[7:0]
X 00000000
Resets (Above)
Register
UBCR14
Bits Name Description
31:8 (Reserved)
7:0 BC
Byte Count (read-only).
Number of bytes in the FIFO is Byte Count plus 1 (BC+1).