All,

 When I used the PIC 12C672 as a pulse generator on the project
 I was working on, one of the engineers wanted to use a 556.
 The cost of the PIC was less than the cost of the 556 and the
 support components (3 caps and 4-5 resistors), so to replace
 a 555 and it's support components should be about the same.
 And it is more elegant like you say.

                                          Regards,

                                            Jim



On Tue, 07 December 1999, "Paul B. Webster VK2BZC" wrote:

>
> Morgan Olsson wrote:
>
> > Or use an 8pin PIC with internal osc...
> > But the 555 is stronger driver and higher voltage.
>
>   Only to ground.  A major problem with the NE555 is that it doesn't
> pull up to the positive rail, but rather a volt or two short (it is TTL-
> based).
>
>   Amongst other things, this makes it difficult to obtain symmetrical
> square waves (if that is what you want) even using the one-resistor mode
> and correspondingly inaccurate in this mode.
>
>   If you do want accuracy in one-resistor mode, you use a TLC555 (CMOS
> version) but this is then *NOT* as strong a driver as a PIC.
>
>   It's unlikely a 12C508 will be anywhere near as cheap as a NE555,
> but it may rival a TLC555.  It's internal R-C oscillator is probably
> not as accurate over temperature as a TLC555 either, but it is certainly
> more compact (no external components at all), and way more elegant/
> versatile.
>
>   Put a crystal (cheap) and two caps on it and it's *far* more accurate.
> --
>   Cheers,
>         Paul B.

jim@jpes.com