NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
- 679 -
Revision V1.30
NUC97
0
T
E
CHNIC
A
L
RE
F
E
RE
N
CE
MA
NUA
L
Control Endpoint Control Register (USBD_CEPCTL)
Register
Offset
R/W Description
Reset Value
USBD_CEPCTL
0x02C R/W Control Endpoint Control Register
0x0000_0000
31
30
29
28
27
26
25
24
Reserved
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
Reserved
7
6
5
4
3
2
1
0
Reserved
FLUSH
ZEROLEN
STALLEN
NAKCLR
Bits
Description
[31:4]
Reserved
Reserved.
[3]
FLUSH
CEP-fLUSH Bit
0 = No the packet buffer and its corresponding USBD_CEPDATCNT register to be
cleared.
1 = The packet buffer and its corresponding USBD_CEPDATCNT register to be
cleared. This bit is self-cleaning.
[2]
ZEROLEN
Zero Packet Length
This bit is valid for Auto Validation mode only.
0 = No zero length packet to the host during Data stage to an IN token.
1 = USB device controller can send a zero length packet to the host during Data stage
to an IN token. This bit gets cleared once the zero length data packet is sent. So, the
local CPU need not write again to clear this bit.
[1]
STALLEN
Stall Enable Control
When this stall bit is set, the control endpoint sends a stall handshake in response to
any in or out token thereafter. This is typically used for response to invalid/unsupported
requests. When this bit is being set the NAK clear bit has to be cleared at the same time
since the NAK clear bit has highest priority than STALL. It is automatically cleared on
receipt of a next setup-token. So, the local CPU need not write again to clear this bit.
0 = No sends a stall handshake in response to any in or out token thereafter.
1 = The control endpoint sends a stall handshake in response to any in or out token
thereafter.
Note:
Only when CPU writes
data[1:0] is 2’b10 or 2’b00, this bit can be updated.