Ep1 Bulk-Out Transfer (Dual Fifos) - Renesas H8S Family Hardware Manual

Section 22 USB Function Module (USB)

EP1 Bulk-Out Transfer (Dual FIFOs)

OUT token reception

Either of EP1

FIFOs empty?

Data reception from host

Set EP1 FIFO full status

(IFR0.EP1 FULL = 1)

EP1 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 EP1FULL bit in IFR0 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 EP1RDFN bit in TRG and 0 is written to the EP1FULL bit in IFR0. This operation

empties the FIFO that has just been read, and makes it ready to receive the next packet.

Rev. 1.00 Mar. 12, 2008 Page 878 of 1178

REJ09B0403-0100

USB function

Figure 22.15 EP1 Bulk-Out Transfer Operation

Interrupt request

FIFO FULL processing

Read EP1 receive

data size register (EPSZ1)

Read EP1 data

Set EP1 read complete bit

(TRG.EP1 RDFN = 1)

Clear EP1 FIFO full status

(IFR0.EP1 FULL = 0)