SH7721 datasheet(906/1524 Pages) RENESAS

906 / 1524 page

Section 25

USB Function Controller (USBF)

Rev. 3.00 Jan. 18, 2008 Page 844 of 1458

REJ09B0033-0300

• Status Stage (Control-Out)

USB function

Application

IN token reception

0-byte transmission to host

End of control transfer

Set EP0i transmission

complete flag

(IFR0/EP0i TS = 1)

Clear EP0i transfer

request flag

(IFR0/EP0i TR = 0)

Write 1 to EP0i packet

enable bit

(TRG/EP0i PKTE = 1)

Clear EP0i transmission

complete flag

(IFR0/EP0i TS = 0)

End of control transfer

Valid data

in EP0i FIFO?

ACK

Yes

NAK

Interrupt request

Figure 25.10

Status Stage (Control-Out) Operation

The control-out status stage starts with an IN token from the host. When an IN-token is received at

the start of the status stage, there is not yet any data in the EP0i FIFO, and so an EP0i transfer

request interrupt is generated. The application recognizes from this interrupt that the status stage

has started. Next, in order to transmit 0-byte data to the host, 1 is written to the EP0i packet enable

bit but no data is written to the EP0i FIFO. As a result, the next IN token causes 0-byte data to be

transmitted to the host, and control transfer ends.

After the application has finished all processing relating to the data stage, 1 should be written to

the EP0i packet enable bit.

SH7721 Datasheet(PDF) 906 Page - Renesas Technology Corp