Folks!
   Do not be afraid to stick more then one PIC on PCB!
   PCB can carry double!
   With each 16F871 you get about 30 extra I/Os for < $2
in mass purchase. With Atmel Mega or TI MSP it looks even
better.
   Good Luck!
   Mike.

Bob Ammerman wrote:

> A comment was made on this thread that the shift register
> solution required
> many packages vs a CPLD or some such. Here are some counterarguments:
>
> 1: The packages involved are quite small (SO16) and don't
> take up all that
> much space (how big is a 100 pin CPLD).
>
> 2: Since you only have to route a serial and two clock
> signals to each shift
> register, so you can distribute them on the board to be close
> to their point
> of use.
>
> 3: The lower density may permit the user of a 2-layer instead
> of 4-layer (or
> more) board.
>
> Also, the 0.32 price each at 100 drops quite a bit in larger
> quantites. How
> about 0.1875 each in SO16 qty 10000 on tape and reel? That is
> a total of
> 0.1875 * 13 = $2.44 parts cost per board.
>
> Sometimes simple is just what you need.
>
> Bob Ammerman
> RAm Systems
>
>
>
> > Which result in about 4c per output pin.
> >
> > Translated to CPLD, 100 output device should
> > cost 4$. Is this a reasonable price for a 100 output pin
> CPLD (or metal
> mask
> > equivalent) in large quantities ?
> >
> > Tal
> >
> > >
> > >
> > > er... that should be 0.32 each, not 0.032 each.
> > >
> > > Bob
> > >
> > >
> > >
> > > > 74HC595 gives you serial in 8 out with a latch, exactly
> what you need.
> > > >
> > > > 0.032 each at Digikey in 100's 16pin SOIC
> > > >
> > > > Bob Ammerman
> > > > RAm Systems
> > > >
> > > >
> > > >
> > > >
> > > > > beside asics, there are also fpgas, which could eventually be
> > > > > interresting. with an altera 7128, you can get 84 outputs for
> > > about $9,
> > > or
> > > > > if you are happy with 0/3.3V, it drops by $1.
> > > > > for series production, you can migrate an altera design to
> > > clear logic.
> > > > > they produce asics based on fpga designs, with no nre
> cost. this
> drops
> > > the
> > > > > price by about 2.
> > > > >
> > > > >
> > > > >
> > > > > Hello,
> > > > >
> > > > > One of the designs I am working needs many (100 to
> 200) outputs pins
> > > (0/5V
> > > > > signal) controlled by a single mid size PIC. What is
> the cheapest
> way
> > > > > (cents
> > > > > per output pin) adding output pins to a PIC ?
> > > > >
> > > > > This is a mass production product but an ASIC is out of
> > > question at this
> > > > > point.
> > > > >
> > > > > Speed is not an a primary issue so using reasonable serial
> > > communication
> > > > > is
> > > > > OK.
> > > > >
> > > > > Thanks,
> > > > >
> > > > > Tal
> > > > >

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