why the 96x26 dots matrix LCD all dots is on?

My LCD display all dots are on although i had set a entire display off command,why?? because i cant display a character if the dots is on.
Anyone know the reason??

Some LCD are... I don't know the technical term for this. It is something sounds like reverse display. On dots are white, off dots are black.

Is your LCD fall in this category?

Maybe your contrast is set too high and this makes it look like all dots are always on.

No. On is black dots, off is white dots.
i also dunno why cannot off the dots...

Maybe you are missing a power or ground connection to the LCD.

No, nothing missing...
I had checked all the connection, but none of them missing...
But still cannot work...why??

Then what type of LCD is it? Graphic or text? What is the controller in the LCD?

I think by providing more information about your LCD, it would be more easy for people to help you.

I'm using Novatek NT7502 LCD controller which is buit-in for the GDST9633M LCD module, which include 96x26 dots matrix +icon.

And i also using Mitsuibishi M16c microcontroller to interface with the LCD.

But my problem still cannot solve. I already used up 3days to read all the datasheet,still dunno wat happened with my LCD....
headache now.... =(

I observed that my LCD dun have backlight display...is it mean that my LCD somethings wrong???
Is it whenever we switch on the LCD unit, it suppose on the backlight right??? or we need2 control the backlight?? but i cant see any command that to light up backlight in datasheet.

Static build up on the glass can turn dots on. You have an ionizer nearby? Maybe touch the glass with grounded aluminum foil, make sure there is no charge.

To see if a LCD backlight is the problem, put a known character on the screen and hold a flashlight up to it. At the right angle you can see if the expected character is there.

This works great with laptops.

Hi brennbar67,

Do you have a link to the datasheet of the LCD you're using?

Here is the LCD controller datasheet...

The problem i encounter now is my LCD reset pin always go "low" although i set it "high".
And i set the command display off/on & entire display off/on , the LCD still on.... y????

Hi,

You said that your LCD reset pin is not operate correctly. Firstly check you data direction, did you set it to output? Secondly, check the functions of the pin you used to connect to LCD reset. Most of the time, an I/O pin will have several functions multiplex on a single I/O pin. Did you setting it up correctly. For example, some device may have analog function which is the default at power on. You may need to disable the analog in order to get the pin behave as a digital I/O.

Now, my reset pin is ok...
But the LCD still on entire display....although i have set display off command....

Is it the LCD is display function defect??because what ever i display on/off command, the LCD still on... whole screen display..

Hi,

I take a look at the datasheet. I think you need to provide more information.

Some question for you to answer:
1) which interface mode you are using? Data bus 8-bit mode or 16-bit mode? Or serial?
2) How do you set up the LCD driver & power supply cuicuit for the LCD?
3) Did you clear your RAM after initialization?

I think it's nice if you could post a schematic showing how you're setting up your hardware.

Furthermore, it may help people try to help you by providing some code snippet how you're initializing your LCD.

I using 6800 series MPU interface,the data bus is 8bit, parallel data input. Is a master mode.
I using 1/33 duty cycle, internal power supply,use internal oscillator,
step-up x4 voltage cct, normal power mode, LCD bias 1/6, enable chip select.

when power up,i initialize MCU and LCD.

MCU init step:
-declare all the pin&port direction.

LCD init step:
-set reset(put some delay time)
-clear reset pin (delay time)
- select internal power supply(booster,volt regulator&follower cct all are ON)
- display off
-select ADC=0
- select reverse scan (com65- com0)
-select regulator register ratio
-select electronic volume mode
-select electronic register set
-init page
-init start line
-set column addr (H)
-set column addr (L)
-set normal display
-set entire display off
-set display on

After finish,i go display data,b4 display data,i set again the page,colum
-set page
-set column addr
-display my data


i didnt clear the RAM, because the datasheet don't have command to clear the RAM. I think after reset cycle will clear the RAM,right??
Or do you know the way to clear the RAM???

But i have store my data into RAM and callout to display,but still not working....entire display still on.

Clear the RAM means write 0x00 to all RAM location.

Yup, i had tried this method before, but it seem not working.