Michael,

you may want to concider the PIC16C92X family. It has an on board LCD
controller. The controller has its own oscillator, so you can put the
microprocessor into sleep mode and  keep the display running. It also has an
on-board charge pump so you can run the processor at 3V and the display at 5V.

regards,
Paul Beyerl
Technical Sales Mgr.- Future Electronics, Milwaukee

Jason Wolfson wrote:

> Michael,
> driving a raw LCD with a PIC is easy and fun!
> First, is your LCD multiplexed? and by how much? How many segments
> are there? and how many pins? The easiest is a 2:1 multiplexed scheme.
> if your doing HH:MM:SS I would guess you have 6x7=42 segments plus one
> for the colons = 43 plus 2 commons = 45, make that 46, divide by 2
> ... Does your raw LCD have 23 or so pins? then it's 2:1.
> you need to provide 2 square waves to the commons that have 3 states to
> them.
> low, high (5v) and middle (2.5v). No sweat, put a resistor divider network
> on 2 pins, say 10k, that way for 0V, make the pin an output and low, for
> 5V, set the pin high and for 2.5V make the pin an input.....
> for the correct sequence and get a good explanation with diagrams
> look in a Hitachi data book for LCD chips....
> You figure out the segments to light with a look up table, then
> you have to send that data, then the compliment to create an AC drive.
> Any DC component will degrade the LCD life....
> do this from an interrupt to only change the LCD states at 30hz or so and
> your done. Works great....
> good luck
> Jason Wolfson
> jason@lipidex.com
>
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Michael Ghormley
> > Sent: Sunday, June 07, 1998 12:54 AM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: [OT] Voltage and Polarity of an LCD Display
> >
> >
> > I guess this is my night to post to the PICLIST!
> >
> > I have a clock project that needs to display hh:mm:ss on a largish LCD
> > display.  I have found a nice one at a good price (surplus -- no docs or
> > markings of any kind) and got a sample to prototype.  It is a bare (no
> > driver chips) LCD in a kind of huge DIP.  It would be perfect for my
> > purposes.
> >
> > I sat down tonight to begin probing it for the pinouts when I realized
> > that, while I have done any number of HD44780-based projects, I had no
> > idea about driving a "raw" LCD.
> >
> > 1)  What voltage range is typical?  Is 5VDC sufficient?
> >
> > 2)  What about polarity?  Can these things be damaged by reverse
> > polarity?
> >
> > 3)  What about series resistance?  I know these are *very* low amperage
> > devices, but do I need a series resistor with each segment for some
> > reason?  If so, what size?
> >
> > 4)  Is there going to be a chip-wide contrast pin on this thing, or is
> > that up to the hardware that drives it?
> >
> > I did a search with a couple of the search engines, but could not find
> > any info on any 'raw" LCD's.  Any help or advice is appreciated.
> >
> > Michael
> >
> > REMOVE THE .NS (NO SPAM) FROM MY ADDRESS TO REPLY
> > ******************************************************************
> > *******When the way of the Tao is forgotten, kindness and ethics
> > must be taught.
> > Men must learn to pretend to be wise and good.  --  Lao Tzu
> > *************************************************************************
> >