On Tue, Jan 30, 2007 at 08:11:35AM -0500, Olin Lathrop wrote:
> Howard Winter wrote:
> > I think it may be that a lot of people see the 28-pin format as not
> > really a standard choice - because they came from the 16C84 they think
> > of 18 pins as being the "normal" one to use.
> 
> My reasoning was that if you're going to use something the size of a
> QuickProto board anyway, there is no advantage to 18 pins over 28,

I agree with that assessment. Especially when you consider the fact that
the 28 pin package comes in a 300 mil package.

>  whereas 40 pins is considerably more klunky.

When I wirewrap I don't feel there's too much of a difference. But
when breadboarding, the 600 mil package is a problem.

>  I think this logic is still correct,
> but I'm also starting to realize that logic has little to do with it.

Definitely. 

> Apparently there is a comfort level with the 16F84 beyond any reason, and
> anything that looks too different is averted with a shudder and disgust.

I have argued for years that the 16F84's lack of hardware integration makes
it a much more difficult part to use. While items such as PWM, A/D, multiple
timers, comparitors, serial interfaces and the like take a bit more 
learning curve to get up to speed, the ease of use once you do they offer
a huge advantage over doing those same activities in software.

That's why my favorite parts are the ones with the most integration of
peripherals, not the least.

>  I suppose I could have put both the 18 and 28 pin footprints on the 
> board, but

Why?

> I couldn't think of a good reason someone would then use the 18 pin
> footprint, considering the extra one time $1 is small even compared to the
> low price of a QuickProto.  Oh well.

You're right on point here Olin. There's no need for the smaller package
when you buying a prebuilt prototyping board.

> > Personally I
> > tend to use the newer 20/14/8 pin format because they are pin
> > compatible as far as their number of pins goes, so a board using a
> > 20-pin socket, for say the 16F690, can also be used by the 683, 684,
> > 688 8- and 14-pin devices and possibly others,
> 
> I'm glad you're mentioning this.  Here's the part I don't get.  You've
> already bought a QuickProto for $33 and obviously have some other costs in
> parts to make your circuit.  Even if your project could fit in a 16F88, 
> what
> is the big deal about plunking down a 16F876A or something which is a
> complete superset?

The only one I can think of doesn't apply to QuickProto. That is the
internal oscillator and other nanopower facilities. The 16F88 has them
and the 16F876A doesn't. In fact are there any 16F family parts in the 28
and 40 pin form factors that have the same peripheral set as the 16F876/77A
but also include the nanopower tools? I looked at the 16F777 and was almost
sold until I realized that it wasn't self programmable like the 16F877A and
didn't have any data EEPROM.

>  You can ignore the extra I/O lines.  Why isn't a 16F876A

> a 16F88 with dedicated debug lines and a few extra I/O pins to ignore?  Is
> it really the extra $$ or two, or does it just feel wrong, or something
> else?

Just the nanopower and if you have a board that doesn't support it, then it
doesn't really matter, does it?

Snippage...

BAJ
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