R01UH0823EJ0100 Rev.1.00
Page 884 of 1823
Jul 31, 2019
RX23W Group
32. USB 2.0 Host/Function Module (USBc)
32.2.18
Frame Number Register (FRMNUM)
Note 1. To clear the status, write 0 only to the bits to be cleared; write 1 to the other bits.
FRNM[10:0] Flags (Frame Number Flag)
These bits indicate the latest frame number for the USB after the issuing of an SOF packet every 1 ms or writing to the
FRNM[10:0] flags at the SOF packet reception.
CRCE Flag (Receive Data Error Flag)
Indicates whether a CRC error or bit stuffing error has been detected in the pipe during isochronous transfer.
The CRCE flag can be set to 0 by writing 0 to the CRCE flag by software. Here, 1 should be written to the other bits in
FRMNUM.
On detecting a CRC error, the USB generates the internal NRDY interrupt request.
OVRN Flag (Overrun/Underrun Detection Status Flag)
Indicates whether an overrun/underrun error has been detected in the pipe during isochronous transfer.
The OVRN flag can be set to 0 by writing 0 to the OVRN flag by software. Here, 1 should be written to the other bits in
FRMNUM.
(1) When the host controller is selected
The USB sets the OVRN flag to 1 on any of the following conditions.
For the isochronous transfer pipe in the transmitting direction, the time to issue an OUT token comes before all the
transmit data has been written to the FIFO buffer.
For the isochronous transfer pipe in the receiving direction, the time to issue an IN token comes when no FIFO
buffer planes are empty.
(2) When the function controller is selected
The USB sets the OVRN flag to 1 on any of the following conditions.
For the isochronous transfer pipe in the transmitting direction, the IN token is received before all the transmit data
has been written to the FIFO buffer.
For the isochronous transfer pipe in the receiving direction, the OUT token is received when no FIFO buffer planes
are empty.
Address(es): 000A 004Ch
b15
b14
b13
b12
b11
b10
b9
b8
b7
b6
b5
b4
b3
b2
b1
b0
OVRN CRCE
—
—
—
FRNM[10:0]
Value after reset:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Bit
Symbol
Bit Name
Description
R/W
b10 to b0
Frame Number Flag
Latest frame number
R
b13 to b11 —
Reserved
These bits are read as 0. The write value should be 0. R/W
b14
Receive Data Error Flag
0: No error
1: An error occurred
b15
Overrun/Underrun Detection Status
Flag
0: No error
1: An error occurred