Datasheet

MSCAN Controller
Technical Data MC68HC912DT128A — Rev 4.0
342 MSCAN Controller MOTOROLA
18.8.4 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 (CMCR0)).
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 inference within noisy environments.
18.9 Timer Link
The msCAN12 will generate 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 will be generated right after the EOF. A
pulse of one bit time is generated. As the msCAN12 receiver engine
receives also the frames being sent by itself, a timer signal will also be
generated after a successful transmission.
The previously described timer signal can be routed into the on-chip
timer module (ECT). Under the control of the timer link enable (TLNKEN)
bit in the CMCR0, this signal will be connected to the ECT timer channel
m input
(1)
.
After ECT timer has been programmed to capture rising edge events, it
can be used under software control to generate 16-bit time stamps which
can be stored with the received message.
1. The timer channel being used for the timer link for CAN0 is channel 4 and for CAN1 is channel
5.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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