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S9S12G128F0CLF Datasheet, PDF (485/1158 Pages) Freescale Semiconductor, Inc – MC9S12G Family Reference Manual | |||
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Freescaleâs Scalable Controller Area Network (S12MSCANV3)
Module Base + 0x0001
Access: User read/write1
7
R
CANE
W
6
CLKSRC
5
LOOPB
4
LISTEN
3
BORM
2
WUPM
1
SLPAK
0
INITAK
Reset:
0
0
0
1
0
0
0
1
= Unimplemented
Figure 16-5. MSCAN Control Register 1 (CANCTL1)
1 Read: Anytime
Write: Anytime in initialization mode (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)
Table 16-4. CANCTL1 Register Field Descriptions
Field
Description
7
CANE
6
CLKSRC
5
LOOPB
4
LISTEN
3
BORM
2
WUPM
MSCAN Enable
0 MSCAN module is disabled
1 MSCAN module is enabled
MSCAN Clock Source â This bit deï¬nes the clock source for the MSCAN module (only for systems with a clock
generation module; Section 16.4.3.2, âClock System,â and Section Figure 16-43., âMSCAN Clocking Scheme,â).
0 MSCAN clock source is the oscillator clock
1 MSCAN clock source is the bus clock
Loopback Self Test Mode â 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 ï¬eld 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
Listen Only Mode â This bit conï¬gures 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 16.4.4.4, âListen-Only Modeâ). In addition, the error counters are frozen. Listen only mode supports
applications which require âhot pluggingâ 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
Bus-Off Recovery Mode â This bit conï¬gures the bus-off state recovery mode of the MSCAN. Refer to
Section 16.5.2, âBus-Off Recovery,â for details.
0 Automatic bus-off recovery (see Bosch CAN 2.0A/B protocol speciï¬cation)
1 Bus-off recovery upon user request
Wake-Up Mode â If WUPE in CANCTL0 is enabled, this bit deï¬nes whether the integrated low-pass ï¬lter is
applied to protect the MSCAN from spurious wake-up (see Section 16.4.5.5, âMSCAN Sleep Modeâ).
0 MSCAN wakes up on any dominant level on the CAN bus
1 MSCAN wakes up only in case of a dominant pulse on the CAN bus that has a length of Twup
MC9S12G Family Reference Manual, Rev.1.10
Freescale Semiconductor
485
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