CAN 2.0B Controller Module
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
16-9
the system clock and the CAN bit segments. Refer to
Section 16.7, “Programming Model
,” for more
information on the bit timing registers.
Figure 16-5. Relationship between System Clock and CAN Bit Segments
A bit is divided into four separate non-overlapping time segments called SYNC_SEG, PROPSEG, PSEG1,
and PSEG2. These are illustrated in
. The period of the nominal bit time (NBT) is the sum of
the segment durations:
t
NBT
= t
SYNC_SEG
+ t
PROPSEG
+ t
PSEG1
+ t
PSEG2
The sample point indicated in
is the position of the actual sample point if a single sample per
bit is selected (CANCTRL1[SAMP] bit = 0). If three samples per bit are selected, the sample point
indicated in
marks the position of the final sample.
Table 16-8. Example System Clock, CAN Bit Rate, and S-Clock Frequencies
System Clock
Frequency
(MHz)
CAN Bit Rate
(MHz)
Possible S-Clock
Frequency (MHz)
Possible Number of
Time Quanta/Bit
PRESDIV Value + 1
56
1
56
56
1
40
1
40
40
1
25
1
25
25
1
20
1
10, 20
10, 20
2, 1
16
1
8, 16
8, 16
2, 1
56
0.500
56
118
1
40
0.500
40
80
1
25
0.500
25
50
1
20
0.500
1, 2, 2.5
2, 4, 5
20, 10, 8
SYSTEM
CLOCK
S-CLOCK
TIME
QUANTUM
SYNC_SEG
Nominal bit time (NBT)
Sample point
PROPSEG
PSEG1 PSEG2
Transmit
point
Baud Rate Prescaler (PRESDIV)
SS
SS
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...