Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XHY-Family Reference Manual, Rev. 1.01
386
Freescale Semiconductor
The synchronization jump width (see the Bosch CAN 2.0A/B 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 11.3.2.3, “MSCAN Bus Timing Register 0 (CANBTR0)
”
and
Section 11.3.2.4, “MSCAN Bus Timing Register 1 (CANBTR1)
”).
Table 11-37
gives an overview of the Bosch CAN 2.0A/B specification compliant segment settings and the
related parameter values.
NOTE
It is the user’s responsibility to ensure the bit time settings are in compliance
with the CAN standard.
11.4.4
Modes of Operation
11.4.4.1
Normal System Operating Modes
The MSCAN module behaves as described within this specification in all normal system operating modes.
Write restrictions exist for some registers.
Table 11-36. 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 11-37. Bosch CAN 2.0A/B Compliant Bit Time Segment Settings
Time Segment 1
TSEG1
Time Segment 2
TSEG2
Synchronization
Jump Width
SJW
5 .. 10
4 .. 9
2
1
1 .. 2
0 .. 1
4 .. 11
3 .. 10
3
2
1 .. 3
0 .. 2
5 .. 12
4 .. 11
4
3
1 .. 4
0 .. 3
6 .. 13
5 .. 12
5
4
1 .. 4
0 .. 3
7 .. 14
6 .. 13
6
5
1 .. 4
0 .. 3
8 .. 15
7 .. 14
7
6
1 .. 4
0 .. 3
9 .. 16
8 .. 15
8
7
1 .. 4
0 .. 3
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