Fast Real Time Clock

achilles03

I'm trying to mesh two·BS2s that need to sample separate data at a relatively fast rate.· In order to determine what events logged by one·BS2 corrospond to events logged by the second BS2, I'm hoping to insert some sort of reference time (not nessesarily in seconds, possibly in "counts") that they can both access in order to timestamp the data before putting it on an eeprom.· Ideally, I'd like the "unit" of the timer to in the range of 1/100th of a second or less, but 1/10th is doable.· I'd like the·duration before·it resets/rolls back to 0·to be atleast 10 seconds.

What "viable" (aka relatively cheap and easy) options are there for a fast reference clock for both chips?· Can I just get a 555 hitting up a counter?

Thanks in advance!
Dave

Bean

You could make a 555 clock at 1/20th of a second and run that into an 8 bit counter, that will give you a span of 12.8 seconds.
BUT you will need 8 I/O pins on each stamp to read it.

Bean.

Tracy Allen

Will the two Stamps be linked by a wire or something? One Stamp could be the "master" and in its main loop send a timing signal to the "slave". That could be just as accurate as a 555.

There are real time clock chips, such as the PCF8593 that have a programmable frequency output that can be used for timing. If absolute timing accuracy is important.

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Tracy Allen
www.emesystems.com