Freescale Semiconductor, Inc.
MSCAN Controller
17.8.3 msCAN12 POWER_DOWN Mode
The msCAN12 is in POWER_DOWN mode when
• the CPU is in STOP mode or
• the CPU is in WAIT mode and the CSWAI bit is set (see msCAN12
Module Control Register 0 (CMCR0)).
When entering the POWER_DOWN mode, the msCAN12 immediately
stops all ongoing transmissions and receptions, potentially causing CAN
protocol violations.
NOTE: The user is responsible for ensuring that the msCAN12 is not active
when POWER_DOWN mode is entered. The recommended procedure
is to bring the msCAN12 into SLEEP mode before the STOP instruction
(or the WAI instruction, if CSWAI is set) is executed.
To protect the CAN bus system from fatal consequences of violations to
the above rule, the msCAN12 drives the TxCAN pin into recessive state.
In POWER_DOWN mode no registers can be accessed.
17.8.4 Programmable Wake-Up Function
The msCAN12 can be programmed to apply a low-pass filter function to
the RxCAN input line while in SLEEP mode (see control bit WUPM in the
module control register, msCAN12 Module Control Register 1
(CMCR1).). This feature can be used to protect the msCAN12 from
wake-up due to short glitches on the CAN bus lines. Such glitches can
result from electromagnetic interference within noisy environments.
17.9 Timer Link
The msCAN12 generates a timer signal whenever a valid frame has
been received. Because the CAN specification defines a frame to be
valid if no errors occurred before the EOF field has been transmitted
successfully, the timer signal is generated right after the EOF. A pulse of
Advance Information
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68HC(9)12D60 — Rev 4.0
MSCAN Controller
MOTOROLA
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