Newsgroups: comp.robotics
Path: brunix!uunet!usc!elroy.jpl.nasa.gov!ames!agate!iat.holonet.net!bsmall
From: bsmall@iat.holonet.net (Brad Smallridge)
Subject: PICs
Message-ID: <ByJsMv.5Dr@iat.holonet.net>
Organization: HoloNet (BBS: 510-704-1058)
Date: Mon, 30 Nov 1992 21:20:54 GMT
Lines: 54

What do you all think about this article on PIC's?

What's a PIC?  A PIC is a Programmable Integrated Circuit; it's a
microprocessor in a single 18 or 28 pin DIP package including support
circuitry and memory. In your circuits, a PIC needs only +5 Volt, ground,
and a crystal or resistor/capacitor as a timebase generator. With just
this you can program the PIC to perform a video variety of logic, counter,
time delay, data translation, control, or interface functions. An 18 pin
16C54 PIC has 12 general purpose pins that each can be independently
programmed as either input or output.  Where to use a PIC?  A PIC won't
generally replace the microprocessor in a robotics system, unless the
robot is extremely simple. It's internal memory is too limited (only 2K)
and the IO pins are not set up to add on additional memory. There are no
interrupt pins. Neither will it replace your glue chips or faster logic in
a hardware design if speed is a consideration because a PIC's program is
going to be running slower than a logic gate switching. But occasionally
you get a simple little gizmo to design where a micro seems too much
bother and logic gates would number too many. This is the idea place for a
PIC. One such application might be a motor control that counts encoder
counts, calculates a PWM signal, and talks to a host computer. This is an
application that I will follow in upcoming articles. A PIC, which cost
less than $10, may be a lower cost than a fancier motor control chip and
afford some personal touches in the design.  Where to get PIC's I know of
two PIC manufacturers. Microchip makes the 16C5x family and Motorola makes
a 16 pin 68705 PIC. I have access to both programmers and was going to
evaluate both families but decided to concentrate on Microchip for several
reasons. One, the instruction set for the Microchip chips seem closer to
the 8051 family of which I am already familiar. Two, I met the Parallax
people, the ones that develop software and the programmer for the
Microchip PIC's, at the Embedded Systems Conference, and they seemed to be
a good bunch of grass-roots inventor-like people. Three, DigiKey, my
favorite supplier, has recently added the Microchip/Parallax line to their
catalog. My regrets to Motorola. If anyone else can follow this up, we
would all appreciate it.  How much?  The Parallax programmer is $199
including software. You will probably want an EPROM version of the chip
that you select which are around $15 to $22. The One Time Programmable
chips range from $5 to $12. Therefore for about $250 you can get set up
for doing PIC's. You will need an IBM compatible computer with a parallel
port.  Next Month Next month I will look over the PIC architecture and
instruction set.  Brad Smallridge Director San Francisco Robotics Society
of America VOICE (415)550-0588 FAX (415)550-0411 BBS (415) 648-6427 EMAIL
bsmall@holonet.net
 
 
 
 
 
 
 
 
 
 
 

