Dwayne Reid wrote:
> > > Hi Mike, except when you can get 100x 74LS595 shift
> > > regs for 5c each (3c US).
> > > Show me a PIC you can get for 3c?? :o)
> >
> >    So cheap? Of course, I agree, Roman, but not absolutely.
> >Sometimes, I think, PIC with more pins would be better
> >choice taking into account PCB cost etc.
>
> Maybe yes, usually NO.
>
> For example, I have one product that reads a serial (rs-232)
> input and drives 32 LEDs - that's all.  It uses a 12c508 and
> 4- 74hc595 shift registers.  Total cost of those 5 chips is less
> than US $1.50.  There is no way I can get a 40 pin PIC for
> that kind of money.  In addition, the PCB layout was much
> simpler since I could put the LED drivers right next to the
> rows of LEDs.

   I can't agree fully again.
   In small quantities extra dollar doesn't matter. What
does matter - flexibility of 16F871 compared to 12c508
(US $ 3.66 vs US $ 1.07 retail).
   In large quantities you can get considerable discounts.
Not to mention extra cost due to:
- handling in stock extra items:
- placing and soldering extra chips with related components:
- extra PCB dimensions. And it isn't so obvious to me that
  "PCB layout would be much simpler since you could put
   the LED drivers right next to the rows of LEDs", since
   you need extra Vdd, Vss, sync data lines; extra capacitors;

   Even from the point of common sense going kinky way
is not a good practice: There is something kinky in 3c US
for the 74LS595. This price is much less then the chip's
production cost. The real aprox retail price for extra I/O pins
easily could be derived from the comparison:
   US $3.06 - 28-pin 16F870
   US $3.66 - 40-pin 16F871

   By the way, I'm happy with 16F871 working with 9 LEDs,
9 buttons, RS232 and few other I/Os in my project.

   Mike

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