Hyundai HG25504 256X128 LCD display

*Note this page will be updated as I progress with the project*

I picked this display from "All Electronics" - surplus Electronics store for $12(Update now only $6) not a bad price for this size of display, figured for the price worth giving it a shot. Note from the Reviews at All Electronics some people had issues and most after some work got the unit to work. One issue was the display flicker during fast writes, I found that some of this was due to not checking if display was doing a refresh and write timing. When connected via PIO ports to drive it similar to hooking to an Arduino, I got that problem on fast writes When I connected the display directly to the Z80 bus could write faster and none of the dim flicker effects. Could be timing of the Write signal rise and fall times.

Hope this will be helpful for those in the future who get a display that has a SED1330 controller or which library is being used the SED1335 controller which is compatible. A Google search will pull up the SED1335 C library.

While I am connecting it to the Z80, information on my progress of connecting and setting up display would be useful in using with other Micro's.

A few features of the unit:

  • 8080/Z80 compatible bus interface
  • Multiple Planes to mix text and overlay graphics.
  • Virtual display area, allows hardware scrolling and Multiple screens
  • This could allow to do page flips, draw in background so user does not see screen creation.

The datasheet that came with it is a poor photocopy and the PDF's I seen are the same poor photocopy in PDF format. The google the SED1335 since it's compatible is a good clean copy.

/*Update*/ Core library working.



Hardware information

Operating voltage is 5 volts

The sheet states adjustable -25 volts for the LCD bias voltage, I found that about -10.52 ish produces the right contrast on the display. Built a cheep Switching negative power supply i found on the internet that gives up to -14. Will post schematic.

The LCD uses a 8-bit parallel interface as stated compatible with the 8080/Z80 bus. 5 control lines all come off the main 17 pin connector marked J2 on the board.

  1. Frame ground
  2. Vss (ground)
  3. Vdd +5
  4. Vo LCD negative bias voltage Spec says up to -20. (about -10.52 seems to be best so a negative supply source -12 to -15 would work )
  5. /RES active low Reset signal
  6. /RD active low Read LCD
  7. /WR active low Write LCD
  8. /CS Chip select active low
  9. A0 Write Data Low/High Write command (if using directly to bus use CPU address pin zero)
  10. DB0 Data lines
  11. DB1
  12. DB2
  13. DB3
  14. DB4
  15. DB5
  16. DB6
  17. DB7

Interfacing with hardware


This LCD is 8080/Z80 bus compatible can be connected directly to the system bus.