Determining the last event written

Christopher Taylor

I am using the 28335 chip. I have a pin I am monitoring with the ECAPs. I am measuring the rising edge only in continuous mode. The ecap writes the absolute time for the event. According to the documentation the first event is written to CAP1, then to CAP2, then to CAP3, then to CAP4, then back to CAP1. This is done with a mod4 counter. I have a timer that fires and needs to determine the time of the last event. Is there a way to determine which CAP was written to last? I can not find a register to read the mod4 counter. It is expected that the counter will wrap around sometimes so looking for which of the four CAPs the greatest value would not work.

over 15 years ago

0 Arefeen over 15 years ago

Genius 5170 points

Okay .. may be I am not understanding the requirement but can't you store each capture event in a memory buffer and use the memory buffer pointer to determine the last event?

0 Jim MacArthur over 15 years ago

Intellectual 315 points

If you're only interested in the most recent event, and can ignore all preceding events, then perhaps you could set the STOP_WRAP field (bits 2:1) of ECCTL2 to 00. This would wrap the counter to 0 after each event (set CONT/ONSHT to 0), so that all events would get captured into register 1. Will this work for you?

0 Christopher Taylor over 15 years ago in reply to Jim MacArthur

Intellectual 690 points

I will test this later this afternoon. That seems to be exactly what I was looking for. I misunderstood the documentation because of the one shot functionality being so much different than the continuous.

C2000™︎ microcontrollers

C2000 microcontrollers forum

Determining the last event written