Using 16f676 with comms

[NavMicroSystems]

...I have an application which uses a 12F675 (internal Oscillator factory calibrated) which is little more than an Alarm Beeper. It's important to hit the resonant frequency of the Piezo for maximum sound. Now the Piezo is quite tollerant... it likes 4kHz, but is happy from 3.8kHz thru 4.2kHz. Out of every batch of 100 we build, there's always two or three PICs that don't make the grade with the Factory Cal. Now that's a dumb beeper application - and here you want precision async timing with a Factory OSCAL value?

I have several 12F675's running in an NMEA application @4800 Baud on INTOSC.
They run absolutely reliable, but to achieve this you have got to finetune OSCCAL on every single PIC.
Accounting for the time this finetuning takes, I would never do this again.
Today I do not even use resonators on applications where serial comms are involved,
all my never designs include a crystal and two caps.
At the end this is the less expensive solution since it doesn't require any calibration.

[charudatt]

Thank you folks. I guess , I have to redesign the board using 16F72 IC.

Hence forth I shall always remember to use a Xtal where necessary.

regards

Charudatt