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Supply voltage Vdd, what to do with the /RD pin

In the datasheet for the 64128N display it mentions voltages for the various pieces of the display (LCD proper, interface chip, and such) but does not give an actual voltage for the Vdd pin. As the display is already on a PCB my assumption is that that PCB has all of the necessary capacitors and such required by the controller IC to generate all of the necessary voltages except that of Vdd which the user must supply. Can someone tell me what voltage to supply the LCD? On a second note, the datasheet does not supply any information regarding how to connect the display to a typical 8 bit uC like those from NXP/lFreescale, Microchip/Atmel and others. While I can look at the datasheet for the controller not all of the interface pins are available to the user, only some of them. In my case I am using an NXP uC so what should be done about the /RD pin as it is not needed to transmit data to the LCD from the uC.Can someone provide a schematic that shows how to connect the display to my uC (don't need specific ports as they could change when laying out the PCB).

Finally, can anyone provide me with a link to someone in upper management that I could email or even call regarding how technical support is handled?


engineering_seacomp's picture
January 14, 2019


Thank you for contacting us.

Please see the following link for an example of how to interface to the 64128 series display, which should answer your questions.  We don't have any information on connecting to NXP/lFreescale, Microchip/Atmel and others, as there are thousands of micro-controller and micro-processors out there.  You will also see how to connect /RD.

For the Vdd voltage, from the datasheet, you can see the input voltage here:

Please use as this is the email we use for everything internet.






Drwho's picture
January 14, 2019

Hello Engineering_seacomp: Just some feedback. The screen capture of the datasheet you sent says 3V for the LCM. Does it state that the LCM is the Liquid Crystal Module or does it stand for the Logic Control Module (driver chip). I asked my question because the datasheet does not state what LCM stands for. And all of the schematics indicated are for the control modules and don't reflect the outputs from the 64128N PCB which is what I will be connecting to. And regarding using Sales to get my questions answered means I am using the wrong product supplier if the only way to communicate is by the internet. I am not a hobbyist and do work for companies that need quick responses (usually done by phone) so no one has to wait until the next day to get the information needed which result in a waste of time and money. If Displaytech can't see that they need more tech support besides their internet forum then they are serious about working in the industrial machine market. So for the engineer at Seacomp who wrote "Please use as this is the email we use for everything internet." you blame him/her for losing me and my company as a customer. I don't work with people/companies that don't maintain a certain level of professionalism.

Regards Mike.

engineering_seacomp's picture
January 15, 2019

Hi Mike,

The drawings also call out the same information you are looking for.   See page 7 and 8.

 To re-iterate:

and for the backlight:

I apologize for you frustration.  We don't want to get spammed by all the bots on the internet by putting in our personal email, so is what we use for all things internet.  Just like any large company, you must start with the internet as you intial contact, and work your way up the chain for tech support (think "open ticket" process).  It's similiar to you leaving your phone number on this website so we can call you.  You wouldn't want to do that, so email sales, as the first contact.