Low-power universal asynchronous receiver transmitter (LPUART) RM0351
1374/1830 DocID024597 Rev 5
41.4.1 LPUART character description
Word length may be selected as being either 7 or 8 or 9 bits by programming the M[1:0] bits
in the LPUART_CR1 register (see Figure 432).
• 7-bit character length: M[1:0] = 10
• 8-bit character length: M[1:0] = 00
• 9-bit character length: M[1:0] = 01
By default, the signal (TX or RX) is in low state during the start bit. It is in high state during
the stop bit.
These values can be inverted, separately for each signal, through polarity configuration
control.
An Idle character is interpreted as an entire frame of “1”s. (The number of “1”s includes the
number of stop bits).
A Break character is interpreted on receiving “0”s for a frame period. At the end of the
break frame, the transmitter inserts 2 stop bits.
Transmission and reception are driven by a common baud rate generator, the clock for each
is generated when the enable bit is set respectively for the transmitter and receiver.
The details of each block is given below.