
Clock System
MC68HC908GZ60 MC68HC908GZ48 MC68HC908GZ32 Data Sheet, Rev. 6
Freescale Semiconductor
149
The above parameters can be set by programming the bus timing registers, CBTR0 and CBTR1. See
NOTE
It is the user’s responsibility to make sure that the bit timing settings are in
compliance with the CAN standard,
Table 12-8 gives an overview on the CAN conforming segment settings and the related parameter values.
Figure 12-9. Segments Within the Bit Time
.
Table 12-3. Time Segment Syntax
SYNC_SEG
System expects transitions to occur on the bus during this
period.
Transmit point
A node in transmit mode will transfer a new value to the CAN
bus at this point.
Sample point
A node in receive mode will sample the bus at this point. If the
three samples per bit option is selected then this point marks
the position of the third sample.
Table 12-4. CAN Standard Compliant Bit Time Segment Settings
Time
Segment 1
TSEG1
Time
Segment 2
TSEG2
Synchronized
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
SYNC
_SEG
TIME SEGMENT 1
TIME SEG. 2
1
4 ... 16
2 ... 8
8... 25 TIME QUANTA
= 1 BIT TIME
NRZ SIGNAL
SAMPLE POINT
(SINGLE OR TRIPLE SAMPLING)
(PROP_SEG + PHASE_SEG1)
(PHASE_SEG2)