BOB wrote:
> I have done a couple of small project but need help in finding a chip=20
> for a new project.
>
> I need 4 inputs and 4 out puts. The inputs will be switches and 3 of the=
=20
> outputs will be indicator LEDs.  The 4th out put will run a small motor.
>
> What I need help with is what is the smallest PIC Chip I can get by with
>  =20
You need to get a clearer idea of both "smallest" and "get by with" mean=20
in the context of your project.

Does "smallest" mean lowest pin count? smallest physical size? lowest=20
price? lowest power consumption? lowest total cost in both time and money?

Does "get by with" mean "I'm making 10s of thousands of these so i'll=20
put in whatever software development effort is needed to make it work"?=20
or does it mean "I can make it do the task simply and easilly"? or=20
somewhere in between those extremes.

As someone else has suggested there are tricks that would let you use=20
the same IO pins for both inputs and outputs but those tricks come at=20
the price of needing more resistors (you need a resistor to make the=20
input signal weak so the output can overpower it) which take up board=20
space and assembly time. If i'm building boards by hand i'd much rather=20
fit a 14 pin chip than fit an 8-pin chip and extra resistors.  Using the=20
tricks will also increase the software development time and the mental=20
capability required to read and write the software.

There is also the question of software development tools, If you have=20
done all your previous development in assembler for a particular PIC=20
family or using a compiler that only targets a subset of PIC families=20
then you have to decide whether you will stick with what you know and=20
and let it limit your choice of parts or look at the full range of parts=20
and potentially have to learn a new variant of PIC assembler or the=20
quirks of a new compiler.

If you want to program while in circuit you need to be very careful=20
about what you put on the PGC, PGD and VPP lines. If you want to debug=20
in circuit then you either have to use a special debug board sold by=20
microchip or leave the PGC, PGD and VPP lines completely free.

Once you've worked out the answers to those questions then actually=20
finding the part should be pretty easy using the parametric search=20
function on microchip's site.
> requirement
> Must be  5Volt
> need DIP. ( I do not have surface mount abilities)
>
> Bob
>  =20

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.