Swapping LCD panels

[Paolo Predonzani]

> 
> 	A lot of lcd displays used are standard of the shelf parts. I think
> 	they're made (or at least licensed) by Hitachi. They are mainly
> 	alphanumeric (characters on a 5x7 grid) and go for 1x16 characters
> 	upwards.
> 
I have the Samsung databook at home. These LCDs are usually sold in modules
containing an LCD, a controller and some drivers (depending on the size of
the LCD). The modules have a 14 or 15 pin interface. The pin configurations
aren't standard, nevertheless I'll give some hints to try to understand
what pins are connected to what.
The displays I consider are alphanumeric. First, you should look for the
controller. Here is a short cross reference guide:
Samsung KS0066
Hitachi HD44780
OKI MSM6222B
Seiko Epson SED1278F,T7934

I'm not sure if they are pin to pin compatible. They should have 80 pins.
Now you can use a digitar multimeter to check what IC's pins are connected
to the module's interface. So, here are the important pins:
23 GND
33 Vdd
36 RS (register select)
37 R/W
38 Enable
39 D0
40 D1
41 D2
42 D3
43 D4
44 D5
45 D6
46 D7

The ICs have a strange biasing network that I don't understand very well.
However there should be a resistor between pin 30 (bias voltage 5) and a
pin of the interface. This pin can be connected to GND or -5v.

Power supply for backlit displays is connected directly to the display.
A few years ago very strange lamps were used as they needed high voltage
AC power supply.

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| Paolo Predonzani  |  email: predo at dist.dist.unige.it |
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