H8SSLASH2218 datasheet(559/750 Pages) RENESAS

559 / 750 page

Section 14 Universal Serial Bus (USB)

Rev.6.00 Jun. 03, 2008 Page 511 of 698

REJ09B0074-0600

(5) Status Stage (Control-Out)

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

the EP0i packet enable bit.

USB function

Firmware

Receive IN token

Transfer 0-byte data to host

End of control transfer

Set EP0i transmit

complete flag

(EP0iTS in UIFR0 = 1)

Clear EP0i transfer

request flag

(EP0iTR in UIFR0 = 0)

Write 1 to EP0i packet

enable bit

(EP0iPKTE in UTRG0 = 1)

Write 0 to EP0i transfer

request interrupt enable bit

(EP0iTRE in UIER0 = 0)

Clear EP0i transmit

complete flag

(EP0iTS in UIFR0 = 0)

End of control transfer

Valid data

in EP0i FIFO?

ACK

Yes

NAK

EXIRQx

Figure 14.16 Status Stage Operation (Control-Out)

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