EPn_BUF
33
System Level Solutions
January 2013
USB 2.0 (USB20SR) Device IP Core User Guide
Value after Reset:
00000000h
EPn_BUF
The endpoint buffer register holds the buffer pointer for each endpoint. Each
endpoint has two buffer registers, thus allowing double buffering as well as
buffer start address inside the on chip buffer memory. Each buffer register has
3
ROC
Buffer 0 Used
Device sets this bit whenever IN/OUT operation gets completed on an endpoint buffer0.
For IN endpoint, device sets this interrupt bit when it transmits all data from buffer 0 and
buffer 0 is empty. (updated buffer size value of buffer register = 0). For OUT endpoint,
device sets this bit when it receives short data packet or if there is no enough space to
receive other max_packet_size
packet inside the buffer0 at the end of the packet
receive operation. It also sets the buffer used bit of the buffer0 register of
the endpoint
before this interrupt is set high.
1: Operation is completed on buffer 0
0: Operation is not completed on buffer 0
Note
: Control endpoint uses single buffer communication for IN and OUT operation.
Device sets buffer0 used bit when out operation is finished.
2
ROC
Unsupported PID error
This interrupt bit is for information purpose only.
Device sets this bit whenever it receives unsupported PID for the endpoint. It means if
endpoint is configured as out endpoint and it receives Token byte for IN operation
selection
.
Device takes necessary action for handling this error.
1: Unsupported PID
is received inside token byte
0: Unsupported PID
is not received inside token byte
1
ROC
Bad packet error
This interrupt bit is for information purpose only. This interrupt receives on OUT endpoint
only.
Device sets this bit whenever it receives data packet with CRC16 error.
1: Data packet is received with CRC16 error.
0: Data packet is not received with CRC16 error.
0
ROC
Time out error
This interrupt bit is for information purpose only.
Device sets this bit on different condition for IN and out endpoint. Device sets this bit for
out endpoint when data packet is not received after out token packet within out
operation time out limitation as per the specification. For IN endpoint, device sets this bit
when it does not receive ACK token from host after data packet transmission within IN
operation time out limitation as per the specification. Device takes necessary action to
handle this error.
1: Time out error is received
0: Time out error is not received