MC912DG128A Motorola, MC912DG128A Datasheet - Page 287

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

19-mscan12
MOTOROLA
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.
Above parameters can be set by programming the bus timing registers
(CBTR0–1, see
msCAN12 Bus Timing Register 1
It is the user’s responsibility to make sure that his 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 under-lying concepts please 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 long.
MSCAN Controller
msCAN12 Bus Timing Register 0 (CBTR0)
(CBTR1)).
Figure 49
gives an overview on the
MC68HC912DT128A Rev 2.0
MSCAN Controller
and
Clock System
1
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