External flip-flop chip to synchronize an external asynchronous input

[EvLer]

Hello everyone,

I am using an external flip-flop chip to synchronize an external asynchronous input into a microcontroller. So, what I am wondering about is how to provide a clock into the FF chip... it has to run at the same rate as the system clock of the microcontroller. Is there a way to take the oscillator clock out on a pin? ... in general that is...
I was also thinking of generating a wave from PWM with unscaled clock and rout it to the FF... or would i have to have a separate crystal oscillator chip? The microcontroller is motorolla 68hc12.
Thanks in advance.

 

[EvLer]

nevermind... found something in the pile of documentation on the core where i can take the clock out on a pin...

 

[berkeman]

Remember that it takes 2 FFs to synchronize the signal. Is the 2nd FF the input into the uC?

 

[EvLer]

Remember that it takes 2 FFs to synchronize the signal. Is the 2nd FF the input into the uC?

yeah, berkeman... THAT i have learned on my own mistake and will not forget. For FFT project i am writting flip-flops in vhdl, no externals.

But this one is a project on speed-detection using microcontroller, in which case i have to use external chips. Seems like it is possible to 'rout out' a clock from the core.