Motorola ColdFire MCF5281 - Manual (Page 491)

FlexCAN
Freescale Semiconductor 25-21
25.5.3 FlexCAN Control Register 1 (CANCTRL1)
Table 25-11 describes the CANCTRL1 fields.
7 6 5 4 3 2 1 0
Field SAMP — TSYNC LBUF LOM PROPSEG
Reset 0000_0000
R/W R/W
Address IPSBAR + 0x1C_0007
Figure 25-8. FlexCAN Control Register 1 (CANCTRL1)
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
acknowledgment or being active on the bus.
0 Regular operation (listen only mode off).
1 Enable listen only mode.
2–0
PROPSE
G
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
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3