Freescale’s Scalable Controller Area Network (S12MSCANV3)
8.3.2.2
MSCAN Control Register 1 (CANCTL1)
The CANCTL1 register provides various control bits and handshake status information of the MSCAN
module as described below.
Module Base + 0x0001
Access: User read/write(1)
7
6
5
4
3
2
1
0
R
SLPAK
INITAK
CANE
W
CLKSRC
LOOPB
LISTEN
BORM
WUPM
Reset:
0
0
0
1
0
0
0
1
= Unimplemented
Figure 8-5. MSCAN Control Register 1 (CANCTL1)
1. Read: Anytime
Write: Anytime in initialization mode (INITRQ = 1 and INITAK = 1); CANE is write once
Table 8-4. CANCTL1 Register Field Descriptions
Field
Description
7
MSCAN Enable
CANE
0 MSCAN module is disabled
1 MSCAN module is enabled
6
MSCAN Clock Source — This bit defines the clock source for the MSCAN module (only for systems with a clock
generation module; Section 8.4.3.2, “Clock System,” and Section Figure 8-43., “MSCAN Clocking Scheme,”).
0 MSCAN clock source is the oscillator clock
CLKSRC
1 MSCAN clock source is the bus clock
5
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 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
LOOPB
1 Loopback self test enabled
4
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 8.4.4.4, “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.
LISTEN
0 Normal operation
1 Listen only mode activated
3
Bus-Off Recovery Mode — This bits configures the bus-off state recovery mode of the MSCAN. Refer to
Section 8.5.2, “Bus-Off Recovery,” for details.
BORM
0 Automatic bus-off recovery (see Bosch CAN 2.0A/B protocol specification)
1 Bus-off recovery upon user request
S12P-Family Reference Manual, Rev. 1.13
Freescale Semiconductor
259
FREESCALE [ Freescale ]
