Programmer’s Model

 

 

 

Table 25-11. CANCTRL1 Field Descriptions

 

 

 

 

Bits

Name

 

Description

 

 

 

 

 

Sampling mode. The SAMP bit determines whether the FlexCAN module will sample each received

 

 

bit one time or three times to determine its value.

7

SAMP

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.

 

 

 

 

 

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).

5

TSYNC

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.

 

 

 

 

 

Lowest buffer transmitted first. The LBUF bit defines the transmit-first scheme.

4

LBUF

0

Message buffer with lowest ID is transmitted first.

 

 

1

Lowest numbered buffer is transmitted first.

 

 

 

 

 

Listen Only Mode. In this mode the FlexCAN is able to receive messages without giving an acknowl-

3

LOM

edgment or being active on the bus.

0

Regular operation (listen only mode off).

 

 

 

 

1

Enable listen only mode.

 

 

 

 

 

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

2–0

PROPSEG

follows:

Propagation Segment Time = (PROPSEG + 1) Time Quanta

 

 

where

 

 

1 Time Quantum = 1 Serial Clock (S-Clock) Period

 

 

 

 

25.5.4 Prescaler Divide Register (PRESDIV)

Field

Reset

R/W

Address

7

0

PRES_DIV

0000_0000

R/W

IPSBAR + 0x1C_0008

Figure 25-9. Prescaler Divide Register (PRESDIV)

Table 25-12describes the PRESDIV fields.

25-24

MCF5282 User’s Manual

MOTOROLA

Page 550
Image 550
Motorola MCF5282 Prescaler Divide Register Presdiv, 12describes the Presdiv fields, CANCTRL1 Field Descriptions, Samp