72F324x2 vs 72F324x6 ICC Problem

dpeter · ‎2006-12-28

Posted on December 28, 2006 at 09:44

dpeter · ‎2006-12-19

Posted on December 19, 2006 at 17:51

I have an application that uses a ST72F324B2. We have been using B6 parts for development, but now are getting ready to use the B2 parts. I have found the warning in the spec sheet is quite explicit when in indicates x2 and x4 parts need Osc1 connected to the ICC and Osc2 grounded. The only problem is that I cannot get the part to work reliably when a resonator is connected, even if I ground Osc2 and connect Osc1 to the ICC connector. It works fine with the resonator removed. The goal is to use the ICC in production, and hopefully without using a B6 part (expensive). Any ideas on how to modify the ICC host circuit to make it robust to the resonator? Any other ideas?

Thanks,

Dave P

wolfgang2399 · ‎2006-12-19

Posted on December 20, 2006 at 07:29

Hi Dave,

I think, it might be a problem with the programmer's configuration. Perhaps it will help to select the programmer configuration ICP OPT Enable with the resonator on the pcb and not connecting the OSC1-pin to ICCCLK nor OSC2 to ground.

I assume you employ the STVP7. In this case you'll find some good information under help - index - ICP.

Best Regards

WoRo

dpeter · ‎2006-12-28

Posted on December 28, 2006 at 09:44

As follow up, the 8/16k parts have different oscillator circuits than the 32 k (at least according to the data sheet) When I put a scope on the resonator leads, the problem went away. I also found I was using loading capacitors (integral to the resonator) that were slightly higher than the recommended values. Placing a 150 pF cap from OSC1 to gnd fixed the problem (and I might try a 1 M ohm resistor as well). I can put these components in the ICC probe.

Thanks for the feedback

Dave P