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ADuC845 Timer2 Capture Mode

Question asked by sean73 on Oct 26, 2011
Latest reply on Nov 16, 2011 by sean73

Hello, I am using the ADuC845 in an embedded design that sync's pps signals from a master (GPS) and slave (atomic clock) device. The INT0 on the ADuC845 will be connected to the GPS pps. The INT1 pin will be connected to an IRQ signal from a MAX3109 for adding 2 more serial ports via SPI. So I don't have any more hardware interrupts available. After the atomic clock is sync'd to the GPS pps signal I would like to confirm with the ADuC845 that the two pps signal are locked in phase. I would like to compare the timing (phase difference) of these two pps signals with the ADuC845 if possible.


I have been reading about the Timer2 in the capture mode for the ADuC845 and this looks like it may be one way that I could accomplish this tasks. However I am not sure how the INT0 pps can be used to compare against with the Timer2 capture functionality? If I had an extra hardware interrupt I think this would be more easily accomplished. So basically I have two pps signals that I would like to compare the pahse difference between. One of them will be connected to INT0, the other could be connected to T2EX in my design. The INT1 pin will be used for an IRQ signal from the MAX3109 IC, so that signal will tie up the second external hardware interrupt. I am not sure if I can make an accurate interrupt driven phase comparison betweeen these two pps signals, given the available hardware on the ADuC845. I appreciate any suggestions or thoughts on how this might be accomplisehd with the ADuC845.

thank you,