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Missed TIMER input capture edge interrupt mc9s12xs

Question asked by florijan japelj on Nov 21, 2014
Latest reply on Nov 24, 2014 by florijan japelj

Hello,

 

i have an application in which i have to count 3000 pulses of 120khz input square signal. I am using input capture on timer module to trigger interrupt on positive edge of 120khz input signal. Sometimes one interrupt is not generated and one pulse is not counted. So 3000 pulses lasts for 3001 pulse long. this happens rarely (once per 20s) but it happens. Does anyone have any idea why this is happening. In my application it is critical that interrupts are not missed. The mcu is working on 32Mhz bus clock. Can anyone say what should be the slew rate of measured square signal? Right now it is 50 ns. I am convinced that the there is a hardware problem inside mcu.

 

Best regards,

Florijan

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