25-24
MCF5282 User’s Manual
MOTOROLA
Programmer’s Model
25.5.4 Prescaler Divide Register (PRESDIV)
Table 25-12 describes the PRESDIV fields.
Table 25-11. CANCTRL1 Field Descriptions
Bits
Name
Description
7
SAMP
Sampling mode. The SAMP bit determines whether the FlexCAN 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 1, 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 taken at the
normal sample point and at the two preceding periods of the S-clock.
6
—
Reserved, should be cleared.
5
TSYNC
Timer synchronize mode. The TSYNC bit enables the mechanism that resets the free-running timer
each time a message is received in Message Buffer 0. This feature provides the means to synchro-
nize multiple FlexCAN 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 FlexCAN modules that
are using this feature on the same network.
4
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.
3
LOM
Listen Only Mode. In this mode the FlexCAN is able to receive messages without giving an acknowl-
edgment or being active on the bus.
0 Regular operation (listen only mode off).
1 Enable listen only mode.
2–0
PROPSEG
Propagation segment time. PROPSEG defines the length of the propagation segment in the bit
time. The valid programmed values are 0 to 7. 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
7
0
Field
PRES_DIV
Reset
0000_0000
R/W
R/W
Address
0x1C_0008
Figure 25-9. Prescaler Divide Register (PRESDIV)
Summary of Contents for ColdFire MCF5281
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