908LJ12 - frequency meter

[mohammed]

Hi;

i wanna make a freq. counter, i have been searched for the resolution of the capture module in the datasheet of 908LJ12 controller, but unfortunately i didn't find it's resolution, for example say PIC controllers Capture module with 12.5 nsec.

i need to know what's the resolution of the 908LJ12 controller;

regards

Hasan

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Alban Edit: Part number must be shown in subject line

Message Edited by Alban on 2007-06-27 02:15 AM

[rocco]

Hi Hasan,

If the LJ12 is indeed a member of the HC08 family (I did not verify) and you are running it at 5 volts, then the resolution of the timer is 125 nanoseconds with the maximum bus clock of 8Mhz. But this is not the full story.

To use it as a frequency counter, you will need to service an interrupt per cycle, and that will take over 2 microseconds minimum for each cycle. With background processing, you might be able to measure as fast as 400khz. It may work well for audio.

When I measure frequency, I use a high-speed, pipelined counter in and FPGA, that I then control with the output-compare function of the timer. But I have never needed to measure faster than a few tens of megahertz.

HTH

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Alban Edit: Part number must be shown in subject line


Message Edited by Alban on 2007-06-27 02:15 AM