
EZ-USB FX2 Technical Reference Manual
Page 2-2 EZ-USB FX2 Technical Reference Manual v2.1
2.2 Control Endpoint EP0
Figure 2-1. A USB Control Transfer (With Data Stage)
Endpoint zero accepts a special SETUP packet, which contains an 8-byte data structure that pro-
vides host information about the CONTROL transaction. CONTROL transfers include a final
STATUS phase, constructed from standard PIDs (IN/OUT, DATA1, and ACK/NAK).
Some CONTROL transactions include all required data in their 8-byte SETUP Data packet. Other
CONTROL transactions require more OUT data than will fit into the eight bytes, or require IN data
from the device. These transactions use standard bulk-like transfers to move the data. Note in
Figure 2-1 that the DATA Stage looks exactly like a bulk transfer. As with BULK endpoints, the
endpoint zero byte count registers must be loaded to ACK each data transfer stage of a
CONTROL transfer.
8051 clears HSNAK bit (writes 1 to it)
or
sets the STALL bit.
I
N
A
D
D
R
E
N
D
P
C
R
C
5
Token Packet
D
A
T
A
0
8 bytes
Setup
Data
C
R
C
1
6
Data Packet
A
C
K
H/S Pkt
S
E
T
U
P
A
D
D
R
E
N
D
P
C
R
C
5
Token Packet
D
A
T
A
1
Payload
Data
C
R
C
1
6
Data Packet
D
A
T
A
1
Data Pkt
A
C
K
I
N
A
D
D
R
E
N
D
P
C
R
C
5
Token Packet
D
A
T
A
0
Payload
Data
C
R
C
1
6
Data Packet
A
C
K
H/S Pkt
S
Y
N
C
N
A
K
H/S Pkt
O
U
T
A
D
D
R
E
N
D
P
C
R
C
5
Token Packet
C
R
C
1
6
SETUP Stage
SUTOK Interrupt
FX2 sets HSNAK=1
SUDAV Interrupt
DATA Stage
EP0-IN Interrupt EP0-IN Interrupt
STATUS Stage
D
A
T
A
1
O
U
T
A
D
D
R
E
N
D
P
C
R
C
5
Token Packet
C
R
C
1
6
....
H/S Pkt
Data Pkt
A
C
K
H/S Pkt
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