MCBSTM32EXL Keil, MCBSTM32EXL Datasheet - Page 661

• Manufacturer Part Number: MCBSTM32EXL
• Description: BOARD EVALUATION FOR STM32F103ZE
• Manufacturer: Keil

Specifications of MCBSTM32EXL

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RM0008
25.3.3
Note:
Idle characters
Setting the TE bit drives the USART to send an idle frame before the first data frame.
Receiver
The USART can receive data words of either 8 or 9 bits depending on the M bit in the
USART_CR1 register.
Start bit detection
In the USART, the start bit is detected when a specific sequence of samples is recognized.
This sequence is: 1 1 1 0 X 0 X 0X 0X 0 X 0X 0.
Figure 242. Start bit detection
If the sequence is not complete, the start bit detection aborts and the receiver returns to idle
state (no flag is set) waiting for a falling edge.
If only 2 out of the 3 bits are at 0 (sampling on the 3
9
The start bit is confirmed if the last 3 samples are at 0 (sampling on the 8
bits.
Character reception
During an USART reception, data shifts in least significant bit first through the RX pin. In this
mode, the USART_DR register consists of a buffer (RDR) between the internal bus and the
received shift register.
Procedure:
th
and 10
RX state
RX line
Ideal
sample
clock
Real
sample
clock
Conditions
to validate
the start bit
th
bits), the start bit is validated but the NE noise flag bit is set.
1
Falling edge
detection
Universal synchronous asynchronous receiver transmitter (USART)
1
1
0
1
X
X
Doc ID 13902 Rev 9
Idle
2
X
0
3
X
At least 2 bits
out of 3 at 0
X
4
X
7/16
0
5
X
X
X
6
0
7
X
sampled values
At least 2 bits
out of 3 at 0
One-bit time
rd
0 0
8
X
, 5
9
9
th
and 7
0
10 11 12 13 14 15 16
10 11 12 13 14 15 16
X
th
Start bit
X
bits or sampling on the 8
6/16
X
7/16
X
th
X
, 9
th
X
, and 10
ai15471
661/995
th
th
,