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4317I–AVR–01/08
AT90PWM2/3/2B/3B
Figure 19-5. Manchester Frame error detection
Note:
Counter Overflow = MBURR[H:L]
When a Manchester framing error is detected the FEM bit and RxC bit are set at the same time.
This allows the application to execute the reception complete interrupt subroute when this error
conditon is detected.
When a Manchester framing error is detected, the EUSART receiver immediately enters in a
new start bit detection phase. Thus when a Manchester framing error is detected within a frame,
the receiver will process the rest of the frame as a new incomming frame and generate other
FEM errors.
Internal
Manchester
Clock
Start Bit
N2
N1
Bit 1
Start Bit
Bit 2
back shift
Start Bit
N2
N1
Bit 1
Start Bit
front shift
Bit 2
N3
Framing Error
Manchester
Data
Manchester
Decoder
Counter
Internal
Manchester
Clock
Edge Detection
Space
N1/2
Resynchronize
Internal
Manchester
Clock
N2/4
N3
N2/2
Counter
Overflow
Transition outside
the detect window
The counter reaches the counter overflow
value without reaching a manchester edge