FlexCAN Module
Freescale Semiconductor
24-43
PXR40 Microcontroller Reference Manual, Rev. 1
•
SYNC_SEG: This segment has a fixed length of one time quantum. Signal edges are expected to
happen within this section
•
Time Segment 1: This segment includes the Propagation Segment and the Phase Segment 1 of the
CAN standard. It can be programmed by setting the PROPSEG and the PSEG1 fields of the
FLEXCAN_x_CTRL Register so that their sum (plus 2) is in the range of 4 to 16 time quanta
•
Time Segment 2: This segment represents the Phase Segment 2 of the CAN standard. It can be
programmed by setting the PSEG2 field of the FLEXCAN_x_CTRL Register (plus 1) to be 2 to 8
time quanta long
Figure 24-17. Segments within the Bit Time
gives an overview of the CAN compliant segment settings and the related parameter values.
1.
For further explanation of the underlying concepts please refer to ISO/DIS 11519–1, Section 10.3. Reference also the
Bosch CAN 2.0A/B protocol specification dated September 1991 for bit timing.
Table 24-19. Time Segment Syntax
Syntax
Description
SYNC_SEG
System expects transitions to occur on the bus during this period.
Transmit Point
A node in transmit mode transfers a new value to the CAN bus at this point.
Sample Point
A node samples the bus at this point. If the three samples per bit option is
selected, then this point marks the position of the third sample.
Bit
Rate
f
Tq
number
of
Time
Quanta
Þ
Þ
Þ
-----------------------------------------------------------------------------------------
=
Þ
SYNC_SEG
Time Segment 1
Time Segment 2
1
4 ... 16
2 ... 8
8 ... 25 Time Quanta
= 1 Bit Time
NRZ Signal
Sample Point
(single or triple sampling)
(PR PSEG1 + 2)
(PSEG2 + 1)
Transmit Point
Summary of Contents for PXR4030
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