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

----- Original Message -----
From: "Tal Dayan" <tal@ZAPTA.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, June 20, 2002 10:43 AM
Subject: Re: Antwort: [PIC]: cheapest way for adding output pins ?


> 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
>
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Ammerman
> > Sent: Thursday, June 20, 2002 4:29 AM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: Antwort: [PIC]: cheapest way for adding output pins ?
> >
> >
> > er... that should be 0.32 each, not 0.032 each.
> >
> > Bob
> >
> > ----- Original Message -----
> > From: "Bob Ammerman" <rammerman@ADELPHIA.NET>
> > To: <PICLIST@MITVMA.MIT.EDU>
> > Sent: Thursday, June 20, 2002 7:15 AM
> > Subject: Re: Antwort: [PIC]: cheapest way for adding output pins ?
> >
> >
> > > 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
> > >
> > >
> > > ----- Original Message -----
> > > From: "Martin Buehler" <Martin.Buehler@ASCOM.CH>
> > > To: <PICLIST@MITVMA.MIT.EDU>
> > > Sent: Thursday, June 20, 2002 2:32 AM
> > > Subject: Antwort: [PIC]: cheapest way for adding output pins ?
> > >
> > >
> > > > 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.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > Tal Dayan <tal@ZAPTA.COM>
> > > > Gesendet von: pic microcontroller discussion list
> > <PICLIST@MITVMA.MIT.EDU>
> > > > 20.06.02 06:17
> > > > Bitte antworten an pic microcontroller discussion list
> > > >
> > > >
> > > >         An:     PICLIST@MITVMA.MIT.EDU
> > > >         Kopie:
> > > >         Thema:  [PIC]: cheapest way for adding output pins ?
> > > >
> > > >
> > > > 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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> > > >
> > > >
> > >
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> > >
> > >
> >
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