Motorola MCF5281 ユーザーズマニュアル

25-24

MOTOROLA

 

Table 25-12 describes the PRESDIV fields.

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 = (PROPSEG + 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

IPSBAR + 0x1C_0008