RTC to PIC connection

[k7michal]

I've been trying to use a 32.768kHz crystal as the main clock of the PIC mcu and have been running into problems. The chip would get stuck and stop processing.

I've been using it on a bread board and with no 10-15pf grounding caps... Ususally when I use a 4MHz crystal with out caps and on the breadboard I don't get any problems.

Is there a special way of connecting the RTC crystal that is different from a regualar crytal connection?

Many thank you's

 

[Nigel Goodwin]

You should always use capacitors, you may have been lucky with 4MHz crystals - particularly on a breadboard where there is lots of stray capacitance. Why not follow MicroChips recomendations?.

 

[Oznog]

Why stay stuck on that clock crystal?

You can get decent RTC off of a faster crystal. Just set up an interrupt at at some even interval, and just carry remainders.

 

[Nigel Goodwin]

Why stay stuck on that clock crystal?

You can get decent RTC off of a faster crystal. Just set up an interrupt at at some even interval, and just carry remainders.

The usual reason is power consumption, a PIC running off a 32KHz crystal has much lower power consumption - you must also remember to set the config fuses to LP of course.

 

[diode]

You absolutely always should use capacitors. For a 32KHz clock the specs recommend 68 to 100pF.

Also make sure clock setting is LP, that is the one you need at that frequency, you are probably still using a HS or XT, which was fine with a 4Mhz.

EDIT: fine, I didn't see Nigel reply abot the LP was already there...IE cache problem