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Chapter 14 Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XDP512 Data Sheet, Rev. 2.11
624 Freescale Semiconductor
14.3.2.2 MSCAN Control Register 1 (CANCTL1)
The CANCTL1 register provides various control bits and handshake status information of the MSCAN
module as described below.
Read: Anytime
Write: Anytime when INITRQ = 1
and INITAK = 1, except CANE which is write once in normal and
anytime in special system operation modes when the MSCAN is in initialization mode (INITRQ = 1 and
INITAK = 1).
Module Base
+
0x0001
76543210
R
CANE CLKSRC LOOPB LISTEN BORM WUPM
SLPAK INITAK
W
Reset: 00010001
= Unimplemented
Figure 14-4. MSCAN Control Register 1 (CANCTL1)
Table 14-3. CANCTL1 Register Field Descriptions
Field Description
7
CANE
MSCAN Enable
0 MSCAN module is disabled
1 MSCAN module is enabled
6
CLKSRC
MSCAN Clock Source — This bit defines the clock source for the MSCAN module (only for systems with a clock
generation module; Section 14.4.3.2, “Clock System,” and Section Figure 14-42., “MSCAN Clocking Scheme,”).
0 MSCAN clock source is the oscillator clock
1 MSCAN clock source is the bus clock
5
LOOPB
Loopback Self Test Mode — When this bit is set, the MSCAN performs an internal loopback which can be used
for self test operation. The bit stream output of the transmitter is fed back to the receiver internally. The RXCAN
input pin is ignored and the TXCAN output goes to the recessive state (logic 1). The MSCAN behaves as it does
normally when transmitting and treats its own transmitted message as a message received from a remote node.
In this state, the MSCAN ignores the bit sent during the ACK slot in the CAN frame acknowledge field to ensure
proper reception of its own message. Both transmit and receive interrupts are generated.
0 Loopback self test disabled
1 Loopback self test enabled
4
LISTEN
Listen Only Mode — This bit configures the MSCAN as a CAN bus monitor. When LISTEN is set, all valid CAN
messages with matching ID are received, but no acknowledgement or error frames are sent out (see
Section 14.4.5.4, “Listen-Only Mode”). In addition, the error counters are frozen. Listen only mode supports
applications which require “hot plugging” or throughput analysis. The MSCAN is unable to transmit any
messages when listen only mode is active.
0 Normal operation
1 Listen only mode activated
3
BORM
Bus-Off Recovery Mode — This bits configures the bus-off state recovery mode of the MSCAN. Refer to
Section 14.5.2, “Bus-Off Recovery,” for details.
0 Automatic bus-off recovery (see Bosch CAN 2.0A/B protocol specification)
1 Bus-off recovery upon user request