Consider using a CPLD device. I have a tutorial for the Xilinx CPLDs
that includes a project that hooks up (I think) 32 I/O to a Basic Stamp.
The design could easily be expanded to handle more pins in a 95108
device. Two of these would get you there. We don't sell the expander per
se as a product, but our Xilinx prototyping boards are great for getting
started with this type of technology.

The other alternative, since you only need outputs, is a shift register,
but that is a whopping number of packages. The device in the tutorial is
really just a way to gang a bunch of shift registers, but they are all
in one semi-custom chip (and they are fairly cheap). With a CPLD in PLCC
packaging you'd need two. If you were willing to go with surface mount
(like a TQFP package) you could do it in one package plus have enough
spare to do some other things if you wanted to.

The tutorials (along with an Altera and PIC tutorial) are at
http://www.al-williams.com/pictutor

Good luck!

Al Williams
AWC
* Easy RS-232 Prototyping
http://www.al-williams.com/awce/rs1.htm



> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Tal Dayan
> Sent: Wednesday, June 19, 2002 11:18 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [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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