Datasheet

Table Of Contents
Section 15 Universal Serial Bus Interface (USB)
REJ09B0140-0900 Rev. 9.00 Page 511 of 846
Sep 16, 2010
H8S/2215 Group
Note: * When DMA transfers are enabled (EP2oT1 bit set to 1 and EP2oT0 bit set to 0 or 1 in
the UDMAR register), the data in the FIFO is cannot be cleared by writing 1 to
EP2oCLR. To clear the data in the FIFO, first disable DMA transfers (clear the EP2oT1
and EP2oT0 bits in the UDMAR register to 0) and then write 1 to EP2oCLR.
15.3.8 USBFIFO Clear Register 1 (UFCLR1)
UFCLR1 is a one-shot register used to clear the FIFO for each endpoint from EP4 to EP5. Writing
1 to a bit clears the data in the corresponding FIFO. For IN FIFO, writing 1 to a bit in UFCLR1
clears the data for which the corresponding PKTE bit in UTRG1 is cleared to 0 after data write, or
data that is validated by setting the corresponding PKTE bit in UTRG1. For OUT FIFO, writing 1
to a bit in UFCLR1 clears data that has not been fixed during reception or received data for which
the corresponding read completion bit is not set to 1. Accordingly, care must be taken not to clear
data that is currently being received or transmitted. EP4i and EP4o FIFOs, having a dual FIFO
configuration, are cleared by entire FIFOs. Note that this trigger does not clear the corresponding
interrupt flag. For information on accessing this register, see 2.9.4, Accessing Registers
Containing Write-Only Bits.
Bit Bit Name Initial Value R/W Description
7 to 3
All 0
R
Reserved
These bits are always read as 0 and cannot be
modified.
2
EP5iCLR
0
W
EP5i clear
0: Performs no operation
1: Clears EP5i IN FIFO
1
EP4oCLR
0
W
EP4o clear*
0: Performs no operation
1: Clears EP4o OUT FIFO
0
EP4iCLR
0
W
EP4i clear
0: Performs no operation
1: Clears EP4i IN FIFO
Note: * When DMA transfers are enabled (EP4oT1 bit set to 1 and EP4oT0 bit set to 0 or 1 in
the UDMAR register), the data in the FIFO is cannot be cleared by writing 1 to
EP4oCLR. To clear the data in the FIFO, first disable DMA transfers (clear the EP4oT1
and EP4oT0 bits in the UDMAR register to 0) and then write 1 to EP4oCLR.