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Chapter 16 Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XE-Family Reference Manual , Rev. 1.07
668
Freescale Semiconductor
The synchronization jump width (see the Bosch CAN specification for details) can be programmed in a
range of 1 to 4 time quanta by setting the SJW parameter.
The SYNC_SEG, TSEG1, TSEG2, and SJW parameters are set by programming the MSCAN bus timing
registers (CANBTR0, CANBTR1) (see
Section 16.3.2.3, “MSCAN Bus Timing Register 0 (CANBTR0)
”
and
Section 16.3.2.4, “MSCAN Bus Timing Register 1 (CANBTR1)
”).
Table 16-35
gives an overview of the CAN compliant segment settings and the related parameter values.
NOTE
Itistheuser’sresponsibilitytoensurethebittimesettingsareincompliance
with the CAN standard.
16.4.4
Modes of Operation
16.4.4.1
Normal Modes
The MSCAN module behaves as described within this specification in all normal system operation modes.
16.4.4.2
Special Modes
The MSCAN module behaves as described within this specification in all special system operation modes.
Table 16-34. Time Segment Syntax
Syntax
Description
SYNC_SEG
System expects transitions to occur on the CAN 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 in receive mode samples the CAN bus at this point. If the
three samples per bit option is selected, then this point marks the
position of the third sample.
Table 16-35. CAN Standard Compliant Bit Time Segment Settings
Time Segment 1
TSEG1
Time Segment 2
TSEG2
Synchronization
Jump Width
SJW
5 .. 10
4 .. 11
5 .. 12
6 .. 13
7 .. 14
8 .. 15
9 .. 16
4 .. 9
3 .. 10
4 .. 11
5 .. 12
6 .. 13
7 .. 14
8 .. 15
2
3
4
5
6
7
8
1
2
3
4
5
6
7
1 .. 2
1 .. 3
1 .. 4
1 .. 4
1 .. 4
1 .. 4
1 .. 4
0 .. 1
0 .. 2
0 .. 3
0 .. 3
0 .. 3
0 .. 3
0 .. 3