FlexCAN
30-5
Freescale Semiconductor
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
30.1.3.5
Listen-only Mode
In listen-only mode, transmission is disabled, all error counters are frozen and the module operates in a
CAN error passive mode. Only messages acknowledged by another CAN station are received. If FlexCAN
detects a message that has not been acknowledged, it flags a BIT0 error (without changing the REC), as if
it was trying to acknowledge the message. Because the module does not influence the CAN bus in this
mode, the device is capable of functioning like a monitor or for automatic bit-rate detection.
30.2
External Signal Description
Each FlexCAN module has two I/O signals connected to the external MPU pins: CANTX and CANRX.
CANTX transmits serial data to the CAN bus transceiver, while CANRX receives serial data from the
CAN bus transceiver.
30.3
Memory Map/Register Definition
The FlexCAN module address space is split into 128 bytes starting at the base address, and 256 bytes
starting at the base a 0x80. Out of the lower 128 bytes, only part is occupied by various registers.
The upper 256 bytes are fully used for the message buffer structures, as described in
Table 30-1. FlexCAN Memory Map
IPSBAR
Offset
Register
Width
(bits)
Affected
by Hard
Reset
Affected
by Soft
Reset
Access
Reset Value
Section/Page
FlexCAN
Supervisor-only Access Registers
0x1C_0000
FlexCAN Module Configuration
Register (CANMCR)
32
Y
Y
R/W
0xD890_000F
Supervisor/User Access Registers
0x1C_0004
FlexCAN Control Register
(CANCTRL)
32
Y
N
R/W
0x0000_0000
0x1C_0008
Free Running Timer (TIMER)
32
Y
Y
R/W
0x0000_0000
0x1C_0010
Rx Global Mask (RXGMASK)
32
Y
N
R/W
0x1FFF_FFFF
0x1C_0014
Rx Buffer 14 Mask (RX14MASk)
32
Y
N
R/W
0x1FFF_FFFF
0x1C_0018
Rx Buffer 15 Mask (RX15MASK)
32
Y
N
R/W
0x1FFF_FFFF
0x1C_001C
Error Counter Register (ERRCNT)
32
Y
Y
R/W
0x0000_0000
0x1C_0020
Error and Status Register
(ERRSTAT)
32
Y
Y
R/W
0x0000_0000
0x1C_0028
Interrupt Mask Register (IMASK)
32
Y
Y
R/W
0x0000_0000
0x1C_0030
Interrupt Flag Register (IFLAG)
32
Y
Y
R/W
0x0000_0000
0x1C_0080
Message Buffers 0–15 (MB0–15)
2048
N
N
R/W
—
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
