H8SSLASH2218 datasheet(563/750 Pages) RENESAS

563 / 750 page

Section 14 Universal Serial Bus (USB)

Rev.6.00 Jun. 03, 2008 Page 515 of 698

REJ09B0074-0600

14.5.7

Bulk-Out Transfer (Dual FIFOs) (Endpoint 2)

EP2 has two 64-byte FIFOs, but the user can receive data and read receive data without being

aware of this dual-FIFO configuration.

When one FIFO is full after reception is completed, the UIFR1/EP2READY bit is set. After the

first receive operation into one of the FIFOs when both FIFOs are empty, the other FIFO is empty,

and so the next packet can be received immediately. When both FIFOs are full, NAK is returned to

the host automatically. When reading of the receive data is completed following data reception, 1

is written to the UTRG0/EP2RDFN bit. This operation empties the FIFO that has just been read,

and makes it ready to receive the next packet.

USB function

Firmware

Receive OUT token

Receive data from host

Set EP2 data ready status

(EP2READY in UIFR1 = 1)

Clear EP2 data ready status

(EP2READY in UIFR1 = 0)

Read USB endpoint receive

data size register 2 (UESZ2)

Read data from USB endpoint

data register 2 (UEDR2)

Write 1 to EP2o read

complete bit

(EP2RDFN in UTRG0 = 1)

Space

in EP2 FIFO?

Yes

Both

EP2 FIFOs empty?

Yes

NAK

ACK

EXIRQx

EXIRQI

Figure 14.19 EP2 Bulk-Out Transfer Operation

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