
RM0008
Universal synchronous asynchronous receiver transmitter (USART)
Doc ID 13902 Rev 12
763/1096
27.3.1
USART block diagram
USART character description
Word length may be selected as being either 8 or 9 bits by programming the M bit in the
USART_CR1 register (see
The TX pin is in low state during the start bit. It is in high state during the stop bit.
An
Idle character
is interpreted as an entire frame of “1”s followed by the start bit of the next
frame which contains data (The number of “1” ‘s will include the number of stop bits).
WAKE
UP
UNIT
RECEIVER
CONTROL
SR
TRANSMIT
CONTROL
TXE TC RXNE IDLE ORE NE FE
USART
CONTROL
INTERRUPT
CR1
M
WAKE
Receive Data Register (RDR)
Receive Shift Register
Read
Transmit Data Register (TDR)
Transmit Shift Register
Write
SW_RX
TX
(DATA REGISTER) DR
TRANSMITTER
CLOCK
RECEIVER
CLOCK
RECEIVER RATE
TRANSMITTER RATE
f
PCLKx(x=1,2)
CONTROL
CONTROL
/16
CONVENTIONAL BAUD RATE GENERATOR
SBK
RWU
RE
TE
IDLE
RXNE
TCIE
TXEIE
CR1
UE
PCE
PS
PEIE
PE
PWDATA
IRLP
SCEN
IREN
DMAR
DMAT
USART Address
CR2
CR3
IrDA
SIR
ENDEC
BLOCK
LINE
CKEN CPOL CPHA LBCL
CK CONTROL
CK
CR2
GT
STOP[1:0]
NACK
DIV_Mantissa
15
0
RE
USART_BRR
/
USARTDIV
TE
HD
(CPU or DMA)
(CPU or DMA)
PRDATA
Hardware
flow
controller
CTS LBD
RX
IRDA_OUT
IRDA_IN
nRTS
nCTS
GTPR
PSC
IE
IE
DIV_Fraction
4
USARTDIV = DIV_Ma (DIV_Fraction / 16)