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Chapter 16
CAN Controller
User’s Manual U16504EE1V1UD00
With TLMODE = 1 the following register settings apply:
The receive-only mode can be used for baudrate detection. Different baudrate configurations can be
tested without disturbing other CAN nodes on the bus.
Differences to CAN protocol in the receive-only mode:
The mode never sends an acknowledge, error frames or transmit messages.
The error counters do not count.
The VALID bit in CANES reports if the DCAN interface receives any valid message.
SAMP defines the number of sample points per bit as specified in the ISO-11898.
SOFC works in conjunction with the SOFE and SOFSEL bits in the CAN Control Register CANC. For
detailed information please refer to the bit description of that SFR register and the time function mode.
Caution:
CPU can read SYNC0/SYNC1 register at any time. Writing to the SYNC0/SYNC1
registers is only allowed during initialization mode. Any write to this register when
INIT is set and the initialization mode is not confirmed by the INITSTATE bit can have
unexpected behavior to the CAN bus.
Register values
BRPRSn = 00h
MASKCn = 00xx xxxxb
SYNC0n = 6Fh
Description
Clock selector = fx
Bit fields
PRMn = 00b
BRPRSn = 0000 0000b
DBTn = 01111b
CAN Bit in TQ = 16
7 < (fx/Baudrate/bit rate prescaler) < 25]
SYNC1n = 1zzz 1101b sample point 75% = 12 TQ:
SJW 25% = 4 TQ
1 TQ equals 1 clock, BRPRS 6, 7 are enabled
z depends on the setting of:
- Number of sampling points
- Receive only function
- Use of time stamp or global time system
SPTn = 01011b
SJWn = 11b
TLMODE = 1
RXONLY
Receive Only Operation
0
Normal operation
1
Only receive operation, CAN does not activate transmit line
SAMP
Bit Sampling
0
Sample receive data one time at receive point
1
Sample receive data three times and take majority decision at
sample point
SOFC
Start of Frame Control
0
SOFE bit is independent from CAN bus activities
1
SOFE bit will be cleared when a message for receive message
4 is received and SOF mode is selected