MC68HC912D60 Motorola, MC68HC912D60 Datasheet - Page 321

• Manufacturer Part Number: MC68HC912D60
• Description: Microcontrollers
• Manufacturer: Motorola

17.10 Clock System
MC68HC912D60A — Rev 3.0
MOTOROLA
receives the frames being sent by itself, a timer signal is also generated
after a successful transmission.
The previously described timer signal can be routed into the on-chip
timer interface module (ECT). This signal is connected to the Timer n
Channel m input
bit in the CMCR0.
After timer n 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.
Figure 17-7
circuitry. With this flexible clocking scheme the msCAN12 is able to
handle CAN bus rates ranging from 10 kbps up to 1 Mbps.
The clock source bit (CLKSRC) in the msCAN12 module control register
(CMCR1) (see
whether the msCAN12 is connected to the output of the crystal oscillator
(EXTALi) or to a clock twice as fast as the system clock (ECLK).
The clock source has to be chosen such that the tight oscillator tolerance
requirements (up to 0.4%) of the CAN protocol are met. Additionally, for
high CAN bus rates (1 Mbps), a 50% duty cycle of the clock is required.
1. The timer channel being used for the timer link is integration dependent.
Freescale Semiconductor, Inc.
For More Information On This Product,
SYSCLK
EXTALi
shows the structure of the msCAN12 clock generation
Go to: www.freescale.com
msCAN12 Bus Timing Register 0
MSCAN Controller
(1)
under the control of the timer link enable (TLNKEN)
Figure 17-7. Clocking Scheme
CLKSRC
CGM
CGMCANCLK
msCAN12
Prescaler
(1...64)
CLKSRC
(CBTR0)) defines
Time quanta
MSCAN Controller
clock
Technical Data
Clock System
321