s908az32ag2cfue Freescale Semiconductor, Inc, s908az32ag2cfue Datasheet - Page 275

• Manufacturer Part Number: s908az32ag2cfue
• Description: M68hc08 Microcontrollers 8-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

A programmable prescaler is used to generate out of the MSCAN08 clock the time quanta (Tq) clock. A
time quantum is the atomic unit of time handled by the MSCAN08.
A bit time is subdivided into three segments
The synchronization jump width (SJW) can be programmed in a range of 1 to 4 time quanta by setting the
SJW parameter.
1. For further explanation of the underlying concepts please refer to ISO/DIS 11 519-1, Section 10.3.
Freescale Semiconductor
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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 PHASE_SEG2 of the CAN standard. It can be
programmed by setting the TSEG2 parameter to be 2 to 8 time quanta long.
CGM
MSCAN08
OSC
÷ 2
CGMXCLK
Figure 24-7. Clocking Scheme
MC68HC908AZ32A Data Sheet, Rev. 2
Bit rate =
PLL
CLKSRC
f
Tq
=
(1)
(see
Presc value
No. of time quanta
f
MSCANCLK
Figure
f
Tq
÷ 2
÷ 2
24-8).
PRESCALER
(1 .. 64)
BCS
(2 * BUS FREQ.)
MSCANCLK
CGMOUT
(TO SIM)
Clock System
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