Systronix 20x4 LCD
Brief Technical Data
July 31, 2000
Here is brief data for the Systronix 20x4 character LCD. It is a DataVision part and uses the
Samsung KS0066 LCD controller. It's a clone of the Hitachi HD44780. We're not aware of any
incompatabilities between the two - at least we have never seen any in all the code and custom
applications we have done.
This 20x4 LCD is electrically and mechanically interchangeable with 20x4 LCDs from several
other vendors. The only differences we've seen among different 20x4 LCDs are:
1) LED backlight brightness, voltage and current vary widely, as does the quality of the display
2) There is a resistor “Rf” which sets the speed of the LCD interface by controlling the internal
oscillator frequency. Several displays we have evaluated have a low resistor value. This makes
the display too slow. Looking at the Hitachi data sheet page 56, it appears that perhaps the
“incorrect” resistor is really intended for 3V use of the displays.
At 5V the resistor Rf should be 91 Kohms. At 3V it should be 75 Kohms. Using a 3V display at
5V is acceptable from a voltage standpoint (the display can operate on 3-5V) but the oscillator
will then be running too slowly. One fix is to always check the busy flag and not use a fixed time
delay in your code, then it will work regardless of the LCD speed. The other option is to always
allow enough delay for the slower display.
All Systronix 20x4 LCDs have the 91 Kohm resistor and are intended for 5V operation.
Thank you for purchasing Systronix embedded control products and accessories. If you have any
other questions please email to support@systronix.com or phone +1-801-534-1017, fax +1-801-
534-1019.