[sci.electronics] What interface do LCDs use?

david@select4.uucp (David Tait) (09/19/89)

Hi all,

I recently bought a liquid-crystal display (LCD) module from a local
electronics junk shop for no better reason than it was cheap, looked
useful and I thought I might learn something about this technology.  The
display is made by Toshiba (model ZQ8045D-101, circa 1986 I'd guess), and
the display area measures 100mm by 275mm.  Unfortunately, there were no
details available, hence the low price.  I might be able to get some
info from Toshiba, but I don't know whether it's an OEM product or only
used in their own micros.  I thought I'd ask the net if anyone knew
anything about such things.

The PCB is littered with surface mount chips (display drivers with
names like M5279 and M5278, a few standards like '244, '390, '163 etc,
and an LA5316, whose function is a mystery).  Connections to the module
are via a 20-way edge connector, and after some scrutiny of the tracks
leading to pins 16 and 8 of the standard chips, plus checking the polarity
of electrolytics connected to the LA5316, I connected a 5V supply (I think
a -5V supply is also used, but I grounded this pin).  Anyway, I was
rewarded by a randomly changing display (vertical bars mostly) when I
touched some of the unconnected edge connector pins.  The display
appears to have 200 rows of 640 pixels (a very useful size).

Discounting power and ground tracks, there seem to be a total of
11 pins which need to be connected (one of these seems to blank the
display).  Just what kind of interface is this?  there are too many pins
if it used serial data with X and Y clocks, and too few pins if it had
direct addressing of X and Y.  My best guess is that it uses a raster mode
with X and Y clocks, X and Y resets (horizontal and vertical sync) and
serial data taken in 4-bit chunks.

I would be very interested to hear from anybody who knows anything about
this module, but I would also welcome general comments about the typical
method of interfacing similar LCD systems.

Thanks for taking the time to read this.

Best wishes, David.
---
David Tait,                   Tel/Fax:   +44-61-275 4504/4512
Electrical Engineering Dept,    JANET:   tait@uk.ac.man.ee.v1
The University,                  UUCP:   ...!mcvax!ukc!muee!tait
Manchester,  M13 9PL,  UK.       AX25:   G0JVY @ GB7NWP

michael@xanadu.COM (Michael McClary) (09/21/89)

In article <6499@ux.cs.man.ac.uk> tait@v1.ee.man.ac.uk writes:
>
>I recently bought a liquid-crystal display (LCD) module from a local
>electronics junk shop []
>
>Discounting power and ground tracks, there seem to be a total of
>11 pins which need to be connected (one of these seems to blank the
>display).

Sounds like 8 data, strobe, acknowlege, and master reset.  As to what
the coding is, try to get a manual.  (I'd try ascii plus graphics
escapes.)

	good luck.

davidc@vlsisj.VLSI.COM (David Chapman) (09/26/89)

In article <6499@ux.cs.man.ac.uk> tait@v1.ee.man.ac.uk (David Tait) writes:
>Hi all,
>
>I recently bought a liquid-crystal display (LCD) module from a local
>electronics junk shop for no better reason than it was cheap, looked
>useful and I thought I might learn something about this technology.  The
>display is made by Toshiba (model ZQ8045D-101, circa 1986 I'd guess), and

I have a couple of displays lying around (also 1986 vintage) that I bought 
on the promise of specs in the mail.  Ha!  They never sent them.  I haven't 
had the time nor inclination to start poking around like you did, but...

>leading to pins 16 and 8 of the standard chips, plus checking the polarity
>of electrolytics connected to the LA5316, I connected a 5V supply (I think
>a -5V supply is also used, but I grounded this pin).  Anyway, I was
>rewarded by a randomly changing display (vertical bars mostly) when I
>touched some of the unconnected edge connector pins.  The display
>appears to have 200 rows of 640 pixels (a very useful size).

Once I _did_ get some specs, but they were for the wrong display!  What
they told me is that I needed +5 and -8 (or -13; I remember seeing 13
somewhere), plus two data lines, plus a clock.  You send in raster data
(another reason I never messed with them; I didn't want to build a 10-
or 20-IC display circuit to go in my homebrew portable) and a bunch of
other stuff.  My display had 11 or so wires too, and I think they used
all of them (at least the similar display in the spec did).

>...  My best guess is that it uses a raster mode
>with X and Y clocks, X and Y resets (horizontal and vertical sync) and
>serial data taken in 4-bit chunks.

You're probably very close to the truth here.  Let me dig up the spec sheet
(if I still have it); if it disagrees with anything I've just said here I'll
repost.

Send me E-mail if you're interested in a Xerox of my spec sheet (assuming
I find it, it's 3rd generation already) and we'll work out postage etc.
-- 
		David Chapman

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