Resonator for Pic28x1

[djmikeys]

I've just ventured into the land of the Pic28x1. I noticed it required a 4mhz resonator, so I bought one some from rapid (order code 90-0545) They only have 2 legs rather than three, will this be the reason for my download circuit not working? Does it need to have 3 legs?

 

[jmumby]

Yep, three leg ceramic type. In saying that it has built in useful yet inaccurate 4mhz resonator.

 

[hippy]

You don't need to use 3-leg resonators but they are easier; they have in-built capacitors between the outer two legs and the centre leg. You can use a two-leg resonator but will need to connect a 33pF cap from each leg to 0V.

A resonator isn't essential for 28X1 operation. It can run at 4MHz or 8MHz without one, but as jmumby notes the timing accuracy won't be as good as when using an external resonator. In most cases that usually doesn't matter.

You can use 4MHz, 8MHz or 16MHz resonators with the 28X1.

http://www.rapidonline.com/Electronic-Components/Frequency-Control/Ceramic-Resonators/3-pin-Ceramic-resonators-(TruXtal)/72967/kw/72967
http://www.rapidonline.com/Electronic-Components/Frequency-Control/Ceramic-Resonators/3-pin-Ceramic-resonators-(ACT)/29222

 

[Dippy]

If you have a couple of 20ish pF caps kicking about you can treat it like crystal.
The DATA SHEET for that device also shows a resistor.
If you haven't got any caps kicking about then you'll just have to order the correct device and learn the lesson. (I've done it myself, you're not alone... )

 

[djmikeys]

Cheers guys, I've got capacitors coming out of my ears so i'll give it a shot.

Mike