at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 277

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

Synchronous Receiver
1790A–ATARM–11/03
Figure 96 and Figure 97 illustrate start detection and character reception when USART oper-
ates in asynchronous mode.
Figure 96. Asynchronous Start Detection
Figure 97. Asynchronous Character Reception
In synchronous mode (SYNC = 1), the receiver samples the RXD signal on each rising edge of
the Baud Rate Clock. If a low level is detected, it is considered as a start. All data bits, the par-
ity bit and the stop bits are sampled and the receiver waits for the next start bit. Synchronous
mode operations provide a high speed transfer capability.
Configuration fields and bits are the same as in asynchronous mode.
Figure 98 illustrates a character reception in synchronous mode.
Clock (x16)
Baud Rate
Sampling
Sampling
Sampling
Baud Rate
Example: 8-bit, Parity Enabled
Detection
Clock
RXD
RXD
Start
Clock
RXD
1
1
2
2
samples
3
3
16
4
4
D0
5
5
samples
16
6
6
D1
Detection
Rejection
7
7
samples
Start
Start
16
8
0
D2
1
1
samples
16
2
2
3
3
D3
samples
4
4
16
5
D4
samples
6
16
7
D5
samples
8
16
9 10 11 12 13 14 15 16
D6
samples
AT91RM3400
16
D7
samples
16
Parity
Bit
samples
16
Stop
Bit
Sampling
D0
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