H8SSLASH2218 datasheet(556/750 Pages) RENESAS

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Section 14 Universal Serial Bus (USB)

Rev.6.00 Jun. 03, 2008 Page 508 of 698

REJ09B0074-0600

(2) Data Stage (Control-In)

The firmware first analyzes the command data that is sent from the host in the setup stage, and

determines the subsequent data stage direction. If the result of command data analysis is that

the data stage is in-transfer, one packet of data to be sent to the host is written to the FIFO. If

there is more data to be sent, this data is written to the FIFO after the data written first has been

sent to the host (EP0iTS in UIFR0 is set to 1).

The end of the data stage is identified when the host transmits an OUT token and the status

stage is entered.

USB function

Firmware

Receive IN token

Transmit data to host

Set EP0i transmit

complete flag

(EP0iTS in UIFR0 = 1)

From setup stage

Write data to USB endpoint

data register 0i (UEDR0i)

Write 1 to EP0i packet

enable bit

(EP0iPKTE in UTRG0 = 1)

Clear EP0i transmit

complete flag

(EP0iTS in UIFR0 = 0)

Write 1 to EP0i packet

enable bit

(EP0iPKTE in UTRG0 = 1)

Write data to USB endpoint

data register 0i (UEDR0i)

1 written

to EP0sRDFN

in UTRG0?

Valid data

in EP0i FIFO?

NAK

Yes

ACK

EXIRQx

Note:

If the size of the data transmitted by the function is smaller than the data size requested by the host,

the function indicates the end of the data stage by returnning to the host a packet shorter than the

maximum packet size. If the size of the data transmitted by the function is an integral multiple of the

maximum packet size, the function indicates the end of the data stage by transmitting a zero-length

packet.

Figure 14.13 Data Stage Operation (Control-In)

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