XC886/888CLM
Controller Area Network (MultiCAN) Controller
User’s Manual
15-19
V1.3, 2010-02
MultiCAN, V1.0
Figure 15-8
Loop-Back Mode
15.1.5.3
Bit Timing Analysis
Detailed analysis of the bit timing can be performed for each CAN node using the
analysis modes of the CAN frame counter. The bit timing analysis functionality of the
frame counter may be used for automatic detection of the CAN baud rate as well as for
the analysis of the timing of the CAN network.
Bit timing analysis is selected by NFCRx.CFMOD = 10
B
. Bit timing analysis does not
affect the operation of the CAN node. The bit timing measurement results are written into
the NFCRx.CFC bit field. Whenever NFCRx.CFC is updated in bit timing analysis mode,
the bit NFCRx.CFCOV is set to indicate the CFC update event. If NFCRx.CFCIE is set,
an interrupt request can be generated (see
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.
CAN node 0
NPCR0.LBM
CAN Bus 0
internal CAN bus
0
1
MultiCAN_loop_back_x2
CAN node 1
NPCR1.LBM
CAN Bus 1
0
1
*