Universal synchronous asynchronous receiver transmitter (USART)
RM0365
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DocID025202 Rev 7
29.8 USART
registers
for a list of abbreviations used in register descriptions.
29.8.1
Control register 1 (USART_CR1)
Address offset: 0x00
Reset value: 0x0000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res.
Res.
Res.
M1
EOBIE RTOIE
DEAT[4:0]
DEDT[4:0]
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
OVER8
CMIE
MME
M0
WAKE
PCE
PS
PEIE
TXEIE
TCIE
RXNEIE IDLEIE
TE
RE
UESM
UE
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
Bits 31:29 Reserved, must be kept at reset value
Bit 28
M1
: Word length
This bit, with bit 12 (M0), determines the word length. It is set or cleared by software.
M[1:0] = 00: 1 Start bit, 8 data bits, n stop bits
M[1:0] = 01: 1 Start bit, 9 data bits, n stop bits
M[1:0] = 10: 1 Start bit, 7 data bits, n stop bits
This bit can only be written when the USART is disabled (UE=0).
Note: In 7-bit data length mode, the Smartcard mode, LIN master mode and Auto baud rate
(0x7F and 0x55 frames detection) are not supported.
Bit 27
EOBIE
: End of Block interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated when the EOBF flag is set in the USART_ISR register
Note: If the USART does not support Smartcard mode, this bit is reserved and forced by
hardware to ‘0’. Please refer to
Section 29.4: USART implementation on page 837
Bit 26
RTOIE
: Receiver timeout interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated when the RTOF bit is set in the USART_ISR register.
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and
forced by hardware to ‘0’.
Section 29.4: USART implementation on page 837
Bits 25:21
DEAT[4:0]
: Driver Enable assertion time
This 5-bit value defines the time between the activation of the DE (Driver Enable) signal and
the beginning of the start bit. It is expressed in sample time units (1/8 or 1/16 bit duration,
depending on the oversampling rate).
This bit field can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept
cleared. Please refer to