Control Transfers - Epson S2R72V18 Technical Manual

1. Functions
1.3.3

Control Transfers

Control transfers for endpoint EP0 are controlled in conjunction with the individual transactions, with
the exception of SetAddress() requests. SetAddress() requests are processed automatically using the
automatic address setup function described later.
Fig. 1-6 illustrates a control transfer for when the data stage is in the OUT direction. (a) The host starts
the control transfer based on the SETUP transaction. The device firmware analyzes request specifics
and prepares to respond to the data stage. (b) The host issues an OUT transaction, the data stage is
performed, and the device receives the data. (c) The host issues an IN transaction, the status stage is
performed, and the device returns a data length zero packet.
Control transfers without a data stage are performed without the data stage shown in this example.
The transition to the status stage is triggered by the host issuing a transaction in the direction opposite
to the data stage. The firmware should be used to monitor the IN_TranNAK status
(D_EP0IntStat.IN_TranNAK bit) and serve as the trigger to change from the data stage to status stage.
Fig. 1-7 illustrates a control transfer for when the data stage is in the IN direction. (a) The host starts
the control transfer based on the results of the SETUP transaction. The device firmware analyzes the
request specifics and prepares to respond to the data stage. (b) The host issues an IN transaction, the
data stage is performed, and the device sends the data. (c) The host issues an OUT transaction, the data
stage is performed, and the device returns an ACK response.
The transition to the status stage is triggered by the host issuing a transaction in the direction opposite
to the data stage. The firmware should be used to monitor the OUT_TranNAK status
(D_EP0IntStat.OUT_TranNAK bit) and serve as the trigger to transition from the data stage to the
status stage.
16
a b
Fig. 1-6 Control transfers when data stage is OUT
b
Host to Device
Device to Host
EPSON
S2R72V18 Technical Manual (Rev.1.00)
c