Universal synchronous asynchronous receiver transmitter (USART)
RM0090
1002/1731
DocID018909 Rev 11
30.6.2
Data register (USART_DR)
Address offset: 0x04
Reset value: 0xXXXX XXXX
30.6.3
Baud rate register (USART_BRR)
Note:
The baud counters stop counting if the TE or RE bits are disabled respectively.
Address offset: 0x08
Reset value: 0x0000 0000
30.6.4
Control register 1 (USART_CR1)
Address offset: 0x0C
Reset value: 0x0000 0000
Bits 31:9 Reserved, must be kept at reset value
Bits 8:0
DR[8:0]
: Data value
Contains the Received or Transmitted data character, depending on whether it is read from
or written to.
The Data register performs a double function (read and write) since it is composed of two
registers, one for transmission (TDR) and one for reception (RDR)
The TDR register provides the parallel interface between the internal bus and the output shift
register (see Figure 1).
The RDR register provides the parallel interface between the input shift register and the
internal bus.
When transmitting with the parity enabled (PCE bit set to 1 in the USART_CR1 register), the
value written in the MSB (bit 7 or bit 8 depending on the data length) has no effect because
it is replaced by the parity.
When receiving with the parity enabled, the value read in the MSB bit is the received parity
bit.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
DIV_Mantissa[11:0]
DIV_Fraction[3:0]
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Bits 31:16 Reserved, must be kept at reset value
Bits 15:4
DIV_Mantissa[11:0]
: mantissa of USARTDIV
These 12 bits define the mantissa of the USART Divider (USARTDIV)
Bits 3:0
DIV_Fraction[3:0]
: fraction of USARTDIV
These 4 bits define the fraction of the USART Divider (USARTDIV). When OVER8=1, the
DIV_Fraction3 bit is not considered and must be kept cleared.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
OVER8
Reserved
UE
M
WAKE
PCE
PS
PEIE
TXEIE
TCIE
RXNEIE IDLEIE
TE
RE
RWU
SBK
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Res.
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