XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 277

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

M68HC12B Family — Rev. 8.0
MOTOROLA
NOTE:
For microcontrollers without the CGM module, CGMCANCLK is driven from the
crystal oscillator (EXTALi).
A programmable prescaler is used to generate out of msCANCLK the time quanta
(Tq) clock. A time quantum is the atomic unit of time handled by the msCAN12.
A bit time is subdivided into three segments
The synchronization jump width can be programmed in a range of 1 to 4 time
quanta by setting the SJW parameter.
These parameters can be set by programming the bus timing registers (CBTR0
and CBTR1). See
msCAN12 Bus Timing Register
It is the user’s responsibility to make sure that the bit time settings are in
compliance with the CAN standard.
CAN-conforming segment settings and the related parameter values.
1. For further explanation of the underlying concepts, refer to ISO/DIS 11519-1, Section 10.3.
•
•
•
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 PROP_SEG and the
PHASE_SEG1 of the CAN standard. It can be programmed by setting the
parameter TSEG1 to consist of 4 to 16 time quanta.
Time segment 2 — This segment represents the PHASE_SEG2 of the CAN
standard. It can be programmed by setting the TSEG2 parameter to be 2 to
8 time quanta.
16.12.3 msCAN12 Bus Timing Register 0
msCAN12 Controller
BitRate
=
f
Tq
---------------------------------------------------------------------------- -
number
1.
=
Table 16-3
-------------------------------------- -
Presc
f
CGMCANCLK
Þ
of
Þ
(1)
f
Þ
value
Tq
:
TimeQuanta
gives an overview on the
and
msCAN12 Controller
16.12.4
Clock System
Data Sheet
277