RM0046 FlexCAN
Doc ID 16912 Rev 5 549/936
Free Running Timer (TIMER)
This register represents a 16-bit free running counter that can be read and written by the
CPU. The timer starts from 0x0000 after Reset, counts linearly to 0xFFFF, and wraps
around.
The timer is clocked by the FlexCAN bit-clock (which defines the baud rate on the CAN bus).
During a message transmission/reception, it increments by one for each bit that is received
or transmitted. When there is no message on the bus, it counts using the previously
programmed baud rate. During Freeze Mode, the timer is not incremented.
The timer value is captured at the beginning of the identifier field of any frame on the CAN
bus. This captured value is written into the Time Stamp entry in a message buffer after a
successful reception or transmission of a message.
Writing to the timer is an indirect operation. The data is first written to an auxiliary register
and then an internal request/acknowledge procedure across clock domains is executed. All
this is transparent to the user, except for the fact that the data will take some time to be
actually written to the register. If desired, software can poll the register to discover when the
data was actually written.
27
LBUF
Lowest Buffer Transmitted First
This bit defines the ordering mechanism for Message Buffer transmission. When asserted, the
LPRIO_EN bit does not affect the priority arbitration.
0 Buffer with highest priority is transmitted first.
1 Lowest number buffer is transmitted first.
28
LOM
Listen-Only Mode
This bit configures FlexCAN to operate in Listen Only Mode. In this mode, transmission is disabled,
all error counters are frozen and the module operates in a CAN Error Passive mode [Ref. 1]. Only
messages acknowledged by another CAN station will be received. If FlexCAN detects a message
that has not been acknowledged, it will flag a BIT0 error (without changing the REC), as if it was
trying to acknowledge the message.
0 Listen Only Mode is deactivated.
1 FlexCAN module operates in Listen Only Mode.
29–31
PROPSEG
Propagation Segment
This 3-bit field defines the length of the Propagation Segment in the bit time. The valid
programmable values are 0–7.
Propagation Segment Time = (PROPSEG + 1) × Time-Quanta.
Time-Quantum = one Sclock period.
1. One time quantum is equal to the Sclock period.
Table 275. CTRL field descriptions (continued)
Field Description
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