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Data about oscillator in internal 4 MHz mode on PIC16F628

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GrandAlf

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pic16f628 int osc

I would like to migrate from 16F84 to 16C628 for the extra pins available, but am not able to find any data of Osc accuracy or stabilty in internal 4 mhz mode. I tend to use serial comms up to 2400, and am a bit concerned about long term performance. Any experiences most welcome.
 

Re: PIC16F628 Int Osc

I use tons of 628 and if you have a good VCC source and temperature variation is not excessive, internal 4mhz is good for rs232.
 

Re: PIC16F628 Int Osc

Thanks for that, must say it looks pretty good at 5v and room temp. Rather suprising really!, appears that it may be ok even for 9600.
 

Re: PIC16F628 Int Osc

My experience is that you should be very careful with internal RC and RS232 because RS232 normally only tolerates 3% frequency offset especially if you have to receive or transmit longer continuous strings of data.

Short strings (max 6 to 8 characters) were always OK in my applications but whenever I have to deal with RS232 I use a crystal now (they are quite inexpensive today) only a pity if you need absolutely all available pins for other tasks ...

hope this helps
 

Ahh what conflicting opinions, I am of course grateful for both sides of the argument. Looking at the graph, it seems like it is well within 3%. Its always nice to have additional pins, I usually only Tx a max of 16 chars, and could restrict myself to 1200 baud, it looks like it could be ok. Guess its worth a try anyway.
 

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