AT32UC3C2512C Automotive Atmel Corporation, AT32UC3C2512C Automotive Datasheet - Page 574

• Manufacturer Part Number: AT32UC3C2512C Automotive
• Manufacturer: Atmel Corporation

25.6.3.3
9166C–AVR-08/11
Asynchronous Receiver
Figure 25-9. Start Frame Delimiter
Drift Compensation
Drift compensation is available only in 16X oversampling mode. An hardware recovery system
allows a larger clock drift. To enable the hardware system, the bit in the MAN register must be
set. If the RXD edge is one 16X clock cycle from the expected edge, this is considered as nor-
mal jitter and no corrective actions is taken. If the RXD event is between 4 and 2 clock cycles
before the expected edge, then the current period is shortened by one clock cycle. If the RXD
event is between 2 and 3 clock cycles after the expected edge, then the current period is length-
ened by one clock cycle. These intervals are considered to be drift and so corrective actions are
automatically taken.
Figure 25-10. Bit Resynchronization
If the USART is programmed in asynchronous operating mode (SYNC = 0), the receiver over-
samples the RXD input line. The oversampling is either 16 or 8 times the Baud Rate clock,
depending on the OVER bit in the Mode Register (MR).
Oversampling
Sampling
16x Clock
point
RXD
Manchester
Manchester
Manchester
encoded
encoded
encoded
data
data
data
Preamble Length
Synchro.
Txd
Txd
Txd
Error
is set to 0
Synchro.
SFD
SFD
SFD
Jump
DATA
One bit start frame delimiter
Expected edge
Tolerance
start frame delimiter
start frame delimiter
DATA
DATA
Command Sync
Jump
Sync
Data Sync
Synchro.
AT32UC3C
Error
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