When I recently designed a battery operated product that uses an LCD
display, I was interested in utilising a serial interface chip to
avoid bogging my microcontroller down with all the extra code and
I/O pins.  However, I was disappointed to discover that the
commercial LCD serial chips that I looked at were quite expensive and
was not really intended for power saving battery applications because
they were running at clock speeds of up to 20 MHZ which make them
draw a lot of power.  I also did not like the idea of dedicating the
serial port of my 8051 design exclusively to driving the LCD display.
 What I needed was an inexpensive chip that runs at a relatively low
clock speed, with a chip select (CS) line which will allow the LCD
serial interface chip to enter sleep mode with a high impedance on
its serial pins for most of the time, and for it to only wake up when
I address the LCD display by pulling the CS line low.  This has a
double advantage of freeing my communications port  the rest of the
time when I don't need to update the LCD as well as bringing current
consumption to an absolute low.

So, I decided to make my own LCD serial interface based on a
PIC16F84 chip running at 4MHz.  It works like a charm!  In fact, I
was so pleased with it that I decided to try and market this to other
design engineers.  But instead of selling it as pre-programmed chips,
I would provide them the option of burning their own chips.  This is
especially intended for manufacturers who want to use this chip as a
production item in their products.  But I also wanted to give
designers the opportunity of trying the chip out before they buy,
and to provide them with free engineering samples design with.
Therefore I decided to market this product almost like a shareware
program.  It works as follows:

A HEX file called DEMF84.HEX contains the shareware program which
you can  program into a PIC16F84 microcontroller to create your own
LCD serial interface chip.   This shareware chip contains all the
features of the actual device, but there is a limit of 1 000 write
actions that you can make to the LCD, before it enters into a mode
prompting you on the display to register the program.   This allows
you to test the chip and even complete the development of your
product with this chip before you spend any money to register it.
Once you are happy that this chip proves usefull to you, you can
register it by sending me the registration fee and  I will provide
you with a HEX file that will enable you to make as many Serial
Interface chips for yourself as you want.

Right now I need people to try out my serial LCD interface and report
any bugs that they find.  I've put together a prelimenary datasheet
in PDF format and zipped it together with the DEMF84.HEX file.  The
whole zip file is 58K big.  If you are interested, then please let
me know by private email, and I will send it to you as an
attachment.   Or even if you are just interested, I would still like
to know about it.  Customization is possible.

Rgds
Werner

http://users.iafrica.com/w/we/wernerte
FOR SALE: Parachute. Only used once, never opened, small stain.
--
Werner Terreblanche     http://users.iafrica.com/w/we/wernerte/index.htm
wterreb@plessey.co.za (work)  OR  wernerte@iafrica.com  (home)
Plessey SA, PO Box 30451,Tokai 7966, Cape Town, South Africa
or at home : Suite 251, PostNet X5061, Stellenbosch, 7599
Tel +27 21 7102251  Fax +27 21 7102886  Home +27 21 8872196
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