SH7721 datasheet(907/1524 Pages) RENESAS

907 / 1524 page

Section 25

USB Function Controller (USBF)

Rev. 3.00 Jan. 18, 2008 Page 845 of 1458

REJ09B0033-0300

25.4.4

EP1 Bulk-Out Transfer (Dual FIFOs)

USB function

Application

OUT token reception

Data reception from host

Set EP1 FIFO full status

(IFR0/EP1 FULL = 1)

Clear EP1 FIFO full status

(IFR0/EP1 FULL = 0)

Read EP1 receive data

size register (EPSZ1)

Read data from EP1

data register (EPDR1)

Write 1 to EP1 read

complete bit

(TRG/EP1 RDFN = 1)

Space

in EP1 FIFO?

Yes

Both

EP1 FIFOs empty?

Yes

NAK

ACK

Interrupt request

Figure 25.11

EP1 Bulk-Out Transfer Operation

EP1 has two 64-byte FIFOs, but the user can perform data reception and receive data reads

without being aware of this dual-FIFO configuration.

When one FIFO is full after reception is completed, the IFR0/EP1 FULL 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, NACK is returned to

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

is written to the TRG/EP1 RDFN bit. This operation empties the FIFO that has just been read, and

makes it ready to receive the next packet.

SH7721 Datasheet(PDF) 907 Page - Renesas Technology Corp