H8SXSLASH1663 datasheet(854/1158 Pages) RENESAS

854 / 1158 page

Section 16 USB Function Module (USB)

Rev.1.00 Jun. 07, 2006 Page 802 of 1102

REJ09B0294-0100

16.5.6

EP2 Bulk-In Transfer (Dual FIFOs)

USB function

Application

IN token reception

Data transmission to host

Clear EP2 transfer

request flag

(IFR0.EP2 TR = 0)

Enable EP2 FIFO

empty interrupt

(IER0.EP2 EMPTY = 1)

IER0.EP2 EMPTY

interrupt

Write one packet of data

to EP2 data register

(EPDR2)

Write 1 to EP2 packet

enable bit

(TRG.EP2 PKTE = 1)

Set EP2

empty status

(IFR0.EP2

EMPTY = 1)

Valid data

in EP2 FIFO?

NACK

ACK

Interrupt request

Yes

Clear EP2 empty status

(IFR0.EP2 EMPTY = 0)

Space

in EP2 FIFO?

Yes

Interrupt

request

Figure 16.16 EP2 Bulk-In Transfer Operation

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

aware of this dual-FIFO configuration. However, one data write is performed for one FIFO. For

example, even if both FIFOs are empty, it is not possible to perform EP2PKTE at one time after

consecutively writing 128 bytes of data. EP2PKTE must be performed for each 64-byte write.

When performing bulk-in transfer, as there is no valid data in the FIFOs on reception of the first

IN token, an EP2TR bit interrupt in IFR0 is requested. With this interrupt, 1 is written to the

EP2EMPTY bit in IER0, and the EP2 FIFO empty interrupt is enabled. At first, both EP2 FIFOs

are empty, and so an EP2 FIFO empty interrupt is generated immediately.

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