r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 1010

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 16 USB Function Module (USB)
16.10.4 Assigning Interrupt Sources to EP0
The EP0-related interrupt sources indicated by the interrupt source bits (bits 0 to 3) in IFR0 must
be assigned to the same interrupt signal with ISR0. The other interrupt sources have no limitations.
16.10.5 Clearing the FIFO When DMA Transfer is Enabled
EPDR1 cannot be cleared when DMA transfer for endpoint 1 is enabled (EP1DMAE in DMAR =
1). Cancel DMA transfer before clearing the register.
16.10.6 Notes on TR Interrupt
Note the following when using the transfer request interrupt (TR interrupt) for IN transfer to EP0i,
EP2, and EP3.
The TR interrupt flag is set if the FIFO for the target EP has no data when the IN token is sent
from the USB host. However, at the timing shown in figure 16.25, multiple TR interrupts occur
successively. Take appropriate measures against malfunction in such a case.
Note: This module determines whether to return NAK if the FIFO of the target EP has no data
Rev. 1.00 Sep. 19, 2008 Page 980 of 1342
REJ09B0467-0100
CPU
Host
USB
when receiving the IN token, but the TR interrupt flag is set after a NAK handshake is
sent. If the next IN token is sent before PKTE of TRG is written to, the TR interrupt flag is
set again.
IN token
Determines whether
to return NAK.
Figure 16.25 TR Interrupt Flag Set Timing
NAK
Sets TR flag
TR interrupt routine
Clear
TR flag
IN token
Determines whether
to return NAK.
Writes
transmit data
NAK
TRG.
PKTE
Sets TR flag
(Sets the flag again)
TR interrupt routine
IN token
Transmits data
ACK