R01UH0823EJ0100 Rev.1.00
Page 864 of 1823
Jul 31, 2019
RX23W Group
32. USB 2.0 Host/Function Module (USBc)
CURPIPE[3:0] Bits (CFIFO Port Access Pipe Specification)
The CURPIPE[3:0] bits specify the pipe number using which data is read or written through the CFIFO port.
After writing to these bits, read these bits to check that the written value agrees with the read value before proceeding to
the next process.
Do not set the same pipe number to the CURPIPE[3:0] bits in the CFIFOSEL, D0FIFOSEL, and D1FIFOSEL registers.
Even if an attempt is made to modify the setting of these bits during access to the FIFO buffer, the current access setting
is retained until the access is completed. Then, the modification becomes effective, thus enabling continuous access.
ISEL Bit (CFIFO Port Access Direction When DCP is Selected)
After writing to the ISEL bit with the DCP being a selected pipe, read this bit to check that the written value agrees with
the read value before proceeding to the next process.
Set this bit and the CURPIPE[3:0] bits simultaneously.
MBW Bit (CFIFO Port Access Bit Width)
The MBW bit specifies the bit width for accessing the CFIFO port.
When the selected pipe is in the receiving direction, once reading data is started after setting this bit, this bit should not
be modified until all the data has been read.
When the selected pipe is in the receiving direction, set the CURPIPE[3:0] bits to a different value once, and then set
these bits and the MBW bit simultaneously. For the procedure for modifying the CURPIPE[3:0] bits, follow the
description of these bits.
When the selected pipe is in the transmitting direction, the bit width cannot be changed from 8-bit width to 16-bit width
while data is being written to the buffer memory.
An odd number of bytes can also be written through byte-access control even when 16-bit width is selected.
REW Bit (Buffer Pointer Rewind)
The REW bit specifies whether or not to rewind the buffer pointer.
When the selected pipe is in the receiving direction, setting the REW bit to 1 while the FIFO buffer is being read allows
re-reading the FIFO buffer from the first data (in double buffer mode, re-reading the currently-read FIFO buffer plane
from the first data is allowed).
Do not set the REW bit to 1 simultaneously with modifying the CURPIPE[3:0] bits. Before setting the REW bit to 1, be
sure to check that the FRDY flag is 1.
To re-write to the FIFO buffer again from the first data for the pipe in the transmitting direction, use the BCLR bit.
