TC1796
Peripheral Units (Vol. 2 of 2)
Controller Area Network (MultiCAN) Controller
User’s Manual 22-36 V2.0, 2007-07
MultiCAN, V2.0
Automatic Baud Rate Detection
For automatic baud rate detection, the time between the observation of subsequent
dominant edges on the CAN bus must be measured. This measurement is automatically
performed if bit field NFCRx.CFSEL = 000
B
. With each dominant edge monitored on the
CAN receive input line, the time (measured in f
CAN
clock cycles) between this edge and
the most recent dominant edge is stored in the NFCRx.CFC bit field.
Synchronization Analysis
The bit time synchronization is monitored if NFCRx.CFSEL = 010
B
. The time between
the first dominant edge and the sample point is measured and stored in the NFCRx.CFC
bit field. The bit timing synchronization offset may be derived from this time as the first
edge after the sample point triggers synchronization and there is only one
synchronization between consecutive sample points.
Synchronization analysis can be used, for example, for fine tuning of the baud rate
during reception of the first CAN frame with the measured baud rate.
Driver Delay Measurement
The delay between a transmitted edge and the corresponding received edge is
measured when NFCRx.CFSEL = 011
B
(dominant to dominant) and
NFCRx.CFSEL = 100
B
(recessive to recessive). These delays indicate the time needed
to represent a new bit value on the physical implementation of the CAN bus.
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