In SX Microcontrollers, SX/B Compiler and SX-Key Tool, veecee42 wrote:

OK, as there is no such thing as a stupid question:

 

I was thinking about building a frequency counter with an sx when I was struck by a different approach; don't know if it might work, but maybe some smart fellas here can comment..

 

traditionally one would use a high clock generator and generate an interrupt with the signal to be measured.. (at least, thats what I think happens).. the only example I found counts up to 15mhz so I assume the interrupt routine than needs 5 clockcycles - what seems plausible  

 

Now I was thinking out of the box:

 

What if we use the frequency to be counted as the clock input and a 4 Mhz crystal oscilator (or other) as an interrupt generator.. and an algorithm that calculates the input clock based on the number of interrupts that have occured over a certain period of 'time' (time being relative to the input clock)?

 

Then we could count up to 75Mhz! Accuracy would off course be limited to a function of the input clock and the interrupt clock, but still quite a performance!!!!

 

Theoretically it seems this could work..

 

any thoughts?

 

greetings,

Vinnie

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