Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!zephyr.ens.tek.com!tektronix!sequent!crg5!cormack
From: cormack@crg5.UUCP (Mike Cormack)
Newsgroups: sci.electronics
Subject: Re^2: PAL's vs gates
Message-ID: <19023@crg5.UUCP>
Date: 7 Feb 90 06:05:50 GMT
References: <358@poppy.warwick.ac.uk> <8590@ingr.com> <2320@dataio.Data-IO.COM>
Organization: Sequent Computer Systems, Beaverton, OR
Lines: 48

aez@Data-IO.COM (Adam Zilinskas) writes:

>Reasons for using PALs:
>1. Inventory. Many of the larger PIC (Programmable IC) chips can emulate
>  any TTL functions that you could use in a design. Its your choice to

Think real estate here too. 1 PAL uses much less space than several
glue logic devices. This can be a crucial in a board design. A reduced
parts count is always a nice idea and PALs can help out immensely.

>2. Board changes (only matters when making PCB, only slightly matters
>  if doing wirewrap). A new PIC and be programmed and patch a circuit
>  within hours/minutes compared to cutting traces on boards and patch

I know this one personally.  Reworking a board stinks and the
reliability decreases quickly once wires are added.  In some cases you
can't add wires.  A primary DFM rule is no wires at FCS and a board
turn if > 4 mod wires need to be added.  It's a competitive world
out there and reliability is very important.  Pals can be much easier
to use for design changes and sometimes are the only choice.

>Reasons for not using PALs:
>1. You have to program them. For productions lines of making thousa
>2. You have to program them. Most of the programming languages for
>3. You have to program them. A hobbyist can go to Radio Crack and get glue

O.K.  we get your point but I think that your not giving H.W.  guys
enough credit (you sound kinda biased ;-).  Gang programmers are great
looking but they're kinda spendy.

Another thing you don't point out is that when a person has to program
a PAL that means they have to touch it.  That's a handling issue which
can cause all kinds of problem for assembly folks.  The first is ESD
and right behind is orientation problems.  At least with glue logic
you can have a machine stuff them in your PCB and a person doesn't
have to touch it.  (That's providing you have an auto-inserter:-)

>I have tried to keep out any overt advertisements about what Data I/O provides

You've given some good advice and a little advert is o.k.  It's good
stuff so some advert is fine.  Some other things.  If your volume is
large enough, you could get a PAL vendor to burn the fuses as they
make it.  They use laser etching for that.  You can solder PALs into
your PCB once your confident that there are no bugs.  (That may take
some time).  Pals can be reliable (less than a 100 PPM).

mike
per yr you could probably have a pal vendor progra