USB Registers
1171
SLAU208Q – June 2008 – Revised March 2018
Copyright © 2008–2018, Texas Instruments Incorporated
USB Module
42.4.3.5 USBOEPBCTY_n Register
Output Endpoint-n X Byte Count Register
This register can be modified only when USBEN = 1.
Figure 42-35. USBOEPBCTY_n Register
7
6
5
4
3
2
1
0
NAK
CNT
rw
rw
rw
rw
rw
rw
rw
rw
Can be modified only when USBEN = 1
Table 42-36. USBOEPBCTY_n Register Description
Bit
Field
Type
Reset
Description
7
NAK
RW
0h
No-acknowledge status bit. The NAK status bit is set by the UBM at the end of a
successful USB out transaction to that endpoint, to indicate that the USB
endpoint-"n" buffer contains a valid data packet, and that the buffer data count
value is valid. When this bit is set, all subsequent transactions to that endpoint
result in a NAK handshake response to the USB host. To re-enable this endpoint
to receive another data packet from the host, this bit must be cleared.
0b = No valid data in buffer. The buffer is ready to receive OUT packets from the
host.
1b = The buffer contains a valid packet from the host, and it has not been picked
up (subsequent host-out requests receive a NAK)
6-0
CNT
RW
0h
Y-buffer data count. The Out_EP-n data count value is set by the UBM when a
new data packet is written to the X-buffer for that out endpoint. It is set to the
number of bytes received in the data buffer.
42.4.3.6 USBOEPSIZXY_n Register
Output Endpoint-n X and Y Buffer Size Register
This register can be modified only when USBEN = 1.
Figure 42-36. USBOEPSIZXY_n Register
7
6
5
4
3
2
1
0
Reserved
SIZx
r0
rw
rw
rw
rw
rw
rw
rw
Can be modified only when USBEN = 1
Table 42-37. USBOEPSIZXY_n Register Description
Bit
Field
Type
Reset
Description
7
Reserved
R
0h
Reserved. Always reads as 0.
6-0
SIZx
RW
0h
Buffer size count. This value needs to be set by software to configure the size of
the X and Y data packet buffers. Both buffers are set to the same size, based on
this value.
000:0000b to 100:0000b are valid numbers for 0 to 64 bytes.
Any value greater than or equal to 100:0001b results in unpredictable results.