MC9S12G FREESCALE [Freescale Semiconductor, Inc], MC9S12G Datasheet - Page 524

• Manufacturer Part Number: MC9S12G
• Description: Ignores external trigger. Performs one conversion sequence and stops.
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Freescale’s Scalable Controller Area Network (S12MSCANV3)
For microcontrollers without a clock and reset generator (CRG), CANCLK is driven from the crystal
oscillator (oscillator clock).
A programmable prescaler generates the time quanta (Tq) clock from CANCLK. A time quantum is the
atomic unit of time handled by the MSCAN.
A bit time is subdivided into three segments as described in the Bosch CAN 2.0A/B specification. (see
Figure
524
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•
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This document is valid for the S12G96 and the S12G128 device. All information related to other devices is preliminary.
16-44):
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.
Transmit Point
SYNC_SEG
1
Bit Rate
NRZ Signal
Figure 16-44. Segments within the Bit Time
MC9S12G Family Reference Manual,
(PROP_SEG + PHASE_SEG1)
Tq
=
=
8 ... 25 Time Quanta
-------------------------------------------------------------------------------- -
(
Time Segment 1
number of Time Quanta
= 1 Bit Time
----------------------------------------------------- -
(
4 ... 16
Prescaler value
f
CANCLK
f
Tq
Rev.1.01
Sample Point
(single or triple sampling)
)
Time Segment 2
(PHASE_SEG2)
2 ... 8
)
Freescale Semiconductor
Eqn. 16-2
Eqn. 16-3