K60P100M100SF2RM Datasheet, PDF (1376/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Functional Description
The PRESDIV field controls a prescaler that generates the Serial Clock (Sclock), whose
period defines the 'time quantum' used to compose the CAN waveform. A time quantum
is the atomic unit of time handled by the CAN engine.
f_Tq
=
fCANCLK
(Prescaler Value)
A bit time is subdivided into three segments² (reference Figure 48-105 and Table
48-118):
• 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 Propagation Segment and the Phase
Segment 1 of the CAN standard. It can be programmed by setting the PROPSEG and
the PSEG1 fields of the CTRL1 Register so that their sum (plus 2) is in the range of 4
to 16 time quanta
• Time Segment 2: This segment represents the Phase Segment 2 of the CAN standard.
It can be programmed by setting the PSEG2 field of the CTRL1 Register (plus 1) to
be 2 to 8 time quanta long
Bit
Rate
=
fTq
(number of Time
Quanta)
NRZ Signal
SYNC_SEG
Time Segment 1
(PROP_SEG + PSEG1 + 2)
Time Segment 2
(PSEG2 + 1)
1
4 ... 16
8 ... 25 Time Quanta
= 1 Bit Time
2 ... 8
Transmit Point
Sample Point
(single or triple sampling)
Figure 48-105. Segments within the Bit Time
2. For further explanation of the underlying concepts please refer to ISO/DIS 11519–1, Section 10.3. Reference also the
Bosch CAN 2.0A/B protocol specification dated September 1991 for bit timing.
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K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.