FlexCAN
Freescale Semiconductor
30-6
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
NOTE
The FlexCAN has no hard-wired protection against invalid bit/field
programming within its registers. Specifically, no protection is provided if
the programming does not meet CAN protocol requirements.
Programming the FlexCAN control registers is typically done during system initialization, prior to the
FlexCAN becoming synchronized with the CAN bus. The configuration registers can be changed after
synchronization by halting the FlexCAN module. This is done when the user sets the CANMCR[HALT]
bit. The FlexCAN responds by setting the CANMCR[NOTRDY] bit.
30.3.1
FlexCAN Configuration Register (CANMCR)
CANMCR defines global system configurations, such as the module operation mode and maximum
message buffer configuration. Most of the fields in this register can be accessed at any time, except the
MAXMB field, which should only be changed while the module is in freeze mode.
IPSBAR
Offset:
0x1C_0000 (CANMCR)
Access: Supervisor
read/write
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
MDIS
FRZ
0
HALT
NOT
RDY
0
SOFT
RST
FRZ
ACK SUPV
0
0
LPM
ACK
0
0
0
0
W
Reset
1
1
0
1
1
0
0
0
1
0
0
1
0
0
0
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
0
0
0
0
MAXMB
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
Figure 30-4. FlexCAN Configuration Register (CANMCR)
Table 30-2. CANMCR Field Descriptions
Field
Description
31
MDIS
Module disable. This bit controls whether FlexCAN is enabled or not. When disabled, FlexCAN shuts down the
FlexCAN clocks that drive the CAN interface and Message Buffer sub-module. This is the only bit in CANMCR not
affected by soft reset. See
Section 30.1.3.3, “Module Disabled Mode,”
for more information.
0 Enable the FlexCAN module, clocks enabled
1 Disable the FlexCAN module, clocks disabled
30
FRZ
Freeze mode enable. When set, the FlexCAN can enter freeze mode when the BKPT line is asserted or the HALT
bit is set. Clearing this bit causes the FlexCAN to exit freeze mode. Refer to
Section 30.1.3.2, “Freeze Mode,”
for
more information.
0 FlexCAN ignores the BKPT signal and the CANMCR[HALT] bit.
1 FlexCAN module enabled to enter debug mode.
29
Reserved, must be cleared.
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60
