Datasheet

MSCAN Controller (MSCAN08)
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
280 Freescale Semiconductor
• Time segment 2: This segment represents PHASE_SEG2 of the CAN standard. It can be
programmed by setting the TSEG2 parameter to be 2 to 8 time quanta long.
The synchronization jump width (SJW) can be programmed in a range of 1 to 4 time quanta by setting the
SJW parameter.
The above parameters can be set by programming the bus timing registers, CBTR0–CBTR1, see 23.13.3
MSCAN08 Bus Timing Register 0 and 23.13.4 MSCAN08 Bus Timing Register 1).
NOTE
It is the user’s responsibility to make sure that the bit timing settings are in
compliance with the CAN standard,
Table 23-8 gives an overview on the CAN conforming segment settings and the related parameter values.
Figure 23-8. Segments within the Bit Time
.
Table 23-3Time 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.
Bit rate=
No. of time quanta
f
Tq
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)