New member
Hi Everyone,

I just purchased the above unit and had a few quick questions. I am looking at section 4 of the data sheet, Absolute Max. Ratings. It is written that the Supply Voltage For LCD Vout is typically -5V, and then bellow in electrical characteristics it says supply voltage for LCD is typically 4.5. I realize that the symbols are different but what exactly is the difference between the 2 terms?

I have gotten the LCD backlight and the contrast to work (I think, not 100% sure what i'm actually looking for, is the black background that occurs when changing the resistance of the pot connected to the contrast what i'm going for?)

I have one pin I am unsure of what to do with it, and I can't find any mention other then the pinout diagram. Pin 7 (NV) is a negative voltage option. Why and how would this be used?

The datasheet says to refer to table 27 for a list of available commands, but I am unable to find a table that looks like what I'm searching for, or one that is labelled as such. Am I just completely missing it, or are they referencing another document other then the unit data sheet?

I had a few questions on what the short forms on the data sheet mean.
AC timing for interface . . .. what does AC refer to ?
I am assuming that E and Chip Select are being interchanged throughout the data sheet
the C not/D on the timing diagram is referring to A0 correct? (data or control)
The E on the timing diagram, is this referring to the chip select? I thought it was but then furthur down
I notice a CS not which made me start wondering.

I am using the PIC16F877 programming with ASM, I'm not sure what i'm going to do with the second chip select yet as all of my I/O are filled. But I will look at that another day.

Thank you very much for any assistance you may offer.

Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.

CF Tech

If you have a "negative voltage output" option module, then pin 7 would be a -5v output (Vee) generated by the module. If your module does not have the "negative voltage output" option, then pin 7 would be open. The module in the image on the page does have the negative voltage circuit on it:

If your module has U3 empty, then there is not a "negative voltage output" option installed.

The LCD "sees" the difference between Vdd (pin 2) and Vo pin 3). If Vdd is 5.0v, and Vo is 0.5v, then Vlcd is 4.5v.

Typically, you connect a 10K ohm pot between Vdd (pin 2) and Vee (pin 7), with the wiper connected to Vo (pin 3). For now please connect it like this, then adjust Vo to +0.5v. That will make it so you can "see" it when the initialization is successful.

AC in this situation means "not DC" and is used to describe the transient signal timing.

Yes, it looks like E1=CS1, E2=CS2.

The controller is a SBN1661G (Epson SED1520 compatible). Here is a link to a copy of the data sheet:

I think with this information, you will at least get a bit further. Give it a shot and post back if you need more information.


New member
Hi CF_Tech,

I changed my POT around and now I have the blackened pixels showing, thank you. I am attempting to write an ASCII character to the screen, but it is not changing from the pixelated view. I have been reading the data sheet, I have tried MCLR on the PIC/LCD and when it restarts still nothing occurs.

I have double checked by wiring on board. I am referencing Figure 24 from the SBN1661 (14.2). From my understanding CS1 or CS2 it doesn't matter what one is utilized it will display it on one side or the other and that is the only difference (i'm just going for a print right now, i don't care about formatting, location etc).
#DEFINE	RW  	        PORTE, 1
#DEFINE CS1 	        PORTE, 2

       ;C/D = 1, E/RD = 1, R/W = 0
       ;A0 = 1,  CS1 = 1, R/W = 0
       bcf CS1
       call delay_1ms
       bsf A0
       call delay_5ms       
       bsf RW
       call delay_5ms
       bsf CS1
       call delay_1ms
       movlw 0x4A
       movwf LCDATA          ;attempt to write 'J'
       call delay_15ms
       bcf CS1
       call delay_5ms
       bcf RW
       call delay_1ms
       bcf A0
       call delay_1ms
      goto $                      ;end of program, repeat forever
Am I referencing the correct chart? I was testing the voltage on my pins and it appears as though the message is latched onto portD of the PIC. Thank you for your time.