On Wed, Jan 21, 2004 at 08:17:03PM +1100, Debbie Hynes wrote:
> Crikey guys!! i didn't mean 2 start a Great Debate like this! :))

Debbie,

You didn't start this debate. It's be on going for two or three years now. I
summarized most of the relevant points on my 16F84 is obsolete page:

http://www.finitesite.com/d3jsys/16F628.html

> I agree the 84 looks a little dated but it still gets the job done. i'm gonna
> use it 4 this proj cuz i'm still learning the f877. the f84 is simple and fast
> 2 do a quick project on, however ... so if it works, use it, hey?

Well here's the issue. You are correct... to a point. The 16F84 does get the
job done. However because of its limitations you have to change your
programming mindset in order to work around those limitations. Software bit
banged UARTS, software PWM, external hardware comparators and A/D, and
virtual software timers because of a lack of real timers are just the tip of
the iceberg. In fact your original project of discussion is a perfect example
to illustrate the point. To wit...

>
> in the meantime, i'll adapt that excellent 555 design till i get the hang of
> using a PIC to generate 38kHz bursts.

The opportunity to figure it out will be lost. If you are hobbyist, like many of
us, most of your projects are one offs. That means that once it works there's
little advantage to go back and redo the project after it's working.

And I'm not sure that's really the point. The real bottom line is that if you
had a newer chip in hand, it's advantageous to take advantage of the "set and
forget" periperals that are available. That's why you're going to gate a 555.
Once the 555 is set to the proper frequency and duty cycle, you no longer have
to devote code space or timing to track that signal. The newer PICs PWM
module is the same: set it up once, then forget about it in your code. It makes
your designs simpler to implement, smaller from a code space perspective and
more robust becuse there's less to debug.

So think about a 16F628A, or a 16F819, or the catch all 16F88 the next time.

BAJ

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