Universal synchronous asynchronous receiver transmitter (USART) RM0351
1222/1693 DocID024597 Rev 3
36.8 USART registers
Refer to Section 1.1 on page 61 for a list of abbreviations used in register descriptions.
36.8.1 Control register 1 (USARTx_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
1514131211109876 5 43210
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 Autobaudrate
(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 USARTx_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 36.4: USART implementation on page 1180.
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 USARTx_ISR register.
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and
forced by hardware to ‘0’. Section 36.4: USART implementation on page 1180.
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 Section 36.4: USART implementation on page 1180.
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