MPC555
/
MPC556
CAN 2.0B CONTROLLER MODULE
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
16-29
16.7.6 Prescaler Divide Register
Table 16-16 CANCTRL1 Bit Descriptions
Bit(s)
Name
Description
0:7
CANCTRL0
8
SAMP
Sampling mode. The SAMP bit determines whether the TouCAN module will sample each
received bit one time or three times to determine its value.
0 = One sample, taken at the end of phase buffer segment one, is used to determine the
value of the received bit.
1 = Three samples are used to determine the value of the received bit. The samples are tak-
en at the normal sample point and at the two preceding periods of the S-clock.
9
—
Reserved
10
TSYNC
Timer synchronize mode. The TSYNC bit enables the mechanism that resets the free-run-
ning timer each time a message is received in message buffer zero. This feature provides
the means to synchronize multiple TouCAN stations with a special “SYNC” message (global
network time).
0 = Timer synchronization disabled.
1 = Timer synchronization enabled.
Note: there can be a bit clock skew of four to five counts between different TouCAN modules
that are using this feature on the same network.
11
LBUF
Lowest buffer transmitted first. The LBUF bit defines the transmit-first scheme.
0 = Message buffer with lowest ID is transmitted first.
1 = Lowest numbered buffer is transmitted first.
12
—
Reserved
13:15
PROPSEG
Propagation segment time. PROPSEG defines the length of the propagation segment in the
bit time. The valid programmed values are zero to seven. The propagation segment time is
calculated as follows:
Propagation Segment Time = (P 1) Time Quanta
where
1 Time Quantum = 1 Serial Clock (S-Clock) Period
PRESDIV —
Prescaler Divide Register
0x30 7088
0x30 7488
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
PRESDIV
CANCTRL2
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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