Internal Oscillator Recalibration

[sahu]

Internal Oscillator Recalibration PIC 16f676

Problems arise if by accident or otherwise, the program memory at address 0x3FF is erased or over written. Since the calibration value is unique to each individual PIC there is no way to know what it was, but it may possible to recover it by recalibrating against a known frequency ?

 

[bigdogguru]

Re: Internal Oscillator Recalibration PIC 16f676

Problems arise if by accident or otherwise, the program memory at address 0x3FF is erased or over written. Since the calibration value is unique to each individual PIC there is no way to know what it was, but it may possible to recover it by recalibrating against a known frequency ?

Yes.

However, it is a nontrivial affair. The issue arises whenever a PIC 16C Series or any "C" variant, windowed devices, are erased with UV which erases the entire storage of the PIC. Therefore, if the OSC Calibration Value is not recorded before hand, well you've got a problem.

The following is an appnote detailing the recalibration of a PIC with an internal RC OSC:


**broken link removed**

A similar approach can be taken with the 16F Series, however it requires precision calibrated test equipment or a "calibrated" calibration rig.

So record your calibration values! I usually affix a label on the bottom side of the device with the value.

 

[ard]

Re: Internal Oscillator Recalibration PIC 16f676

Or alternately, buy or build a Pickit2; it has a tool to re-generate Osccal values.

Regards,

Anand Dhuru

 

[Nick C.]

Re: Internal Oscillator Recalibration PIC 16f676

Or alternately, buy or build a Pickit2; it has a tool to re-generate Osccal values.

Well, well, well - you learn something new every day. Thanks! :grin:

 

[ard]

Sure thing! I too have gone thru the routine of putting stickers under the chip before I got the Pickit2. No more!

Anand

 

[ard]

Some time back, this issue was discussed on another forum I am a member of. Since not everyone uses Pickit2s, this technique will be handy for those who have lost their OSCCAL values. Although the code is in PBP, its a very simple technique that may be written in any language.

Regenerating OSCCAL

Hope this helps someone...

Regards,

Anand Dhuru