MPC555
/
MPC556
CAN 2.0B CONTROLLER MODULE
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
16-30
16.7.7 Control Register 2
Table 16-17 PRESDIV Bit Descriptions
Bit(s)
Name
Description
0:7
PRESDIV
Prescaler divide factor. PRESDIV determines the ratio between the IMB clock frequency and
the serial clock (S-clock). The S-clock is determined by the following calculation:
The reset value of PRESDIV is 0x00, which forces the S-clock to default to the same fre-
quency as the IMB clock. The valid programmed values are 0 through 255.
8:15
CANCTRL2
.
CANCTRL2 —
Control Register 2
0x30 7088
0x30 7488
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
PRESDIV
RJW
PSEG
PSEG2
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Table 16-18 CANCTRL2 Bit Descriptions
Bit(s)
Name
Description
0:7
PRESDIV
See
.
8:9
RJW
Resynchronization jump width. The RJW field defines the maximum number of time quanta
a bit time may be changed during resynchronization. The valid programmed values are zero
through three.
The resynchronization jump width is calculated as follows:
Resynchronizaton Jump Width = (RJW + 1) Time Quanta
10:12
PSEG1
PSEG1[2:0] — Phase buffer segment 1. The PSEG1 field defines the length of phase buffer
segment one in the bit time. The valid programmed values are zero through seven.
The length of phase buffer segment 1 is calculated as follows:
Phase Buffer Segment 1 = (PSEG1 + 1) Time Quanta
13:15
PSEG2
PSEG2 — Phase Buffer Segment 2. The PSEG2 field defines the length of phase buffer seg-
ment two in the bit time. The valid programmed values are zero through seven.
The length of phase buffer segment two is calculated as follows:
Phase Buffer Segment 2 = (PSEG2 + 1) Time Quanta
S-clock
f
SYS
PRESDIV
1
+
------------------------------------
=
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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