
RM0453 Rev 2
RM0453
Low-power universal asynchronous receiver transmitter (LPUART)
1257
36.7.6 LPUART
request
register (LPUART_RQR)
Address offset: 0x18
Reset value: 0x0000 0000
36.7.7
LPUART interrupt and status register [alternate] (LPUART_ISR)
Address offset: 0x1C
Reset value: 0x0080 00C0
The same register can be used in FIFO mode enabled (this section) and FIFO mode
disabled (next section).
FIFO mode enabled
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
TXFRQ RXFRQ MMRQ SBKRQ
Res.
w
w
w
w
Bits 31:5 Reserved, must be kept at reset value.
Bit 4
TXFRQ
: Transmit data flush request
This bit is used when FIFO mode is enabled. TXFRQ bit is set to flush the whole FIFO. This
sets the flag TXFE (TXFIFO empty, bit 23 in the LPUART_ISR register).
Note: In FIFO mode, the TXFNF flag is reset during the flush request until TxFIFO is empty in
order to ensure that no data are written in the data register.
Bit 3
RXFRQ
: Receive data flush request
Writing 1 to this bit clears the RXNE flag.
This enables discarding the received data without reading it, and avoid an overrun condition.
Bit 2
MMRQ
:
Mute mode request
Writing 1 to this bit puts the LPUART in Mute mode and resets the RWU flag.
Bit 1
SBKRQ
: Send break request
Writing 1 to this bit sets the SBKF flag and request to send a BREAK on the line, as soon as
the transmit machine is available.
Note: If the application needs to send the break character following all previously inserted
data, including the ones not yet transmitted, the software should wait for the TXE flag
assertion before setting the SBKRQ bit.
Bit 0 Reserved, must be kept at reset value.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res.
Res.
Res.
Res.
TXFT
RXFT
Res.
RXFF
TXFE
REACK TEACK
WUF
RWU
SBKF
CMF
BUSY
r
r
r
r
r
r
r
r
r
r
r
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Res.
Res.
Res.
Res.
Res.
CTS
CTSIF
Res.
TXFNF
TC
RXFNE
IDLE
ORE
NE
FE
PE
r
r
r
r
r
r
r
r
r
r