Connecting With a TFT Screen

[seasons555copy]

Hi, I have a couple of question about connecting with a RGB TFT Screen.

The screen that I have has a paralled input (24bits for color), a clock, vsync, hsync and a few other connections. The data sheet says that I should have a max clock of 16MHz.

Now my question is can I have a slower clock that stops once in a while, ie a 1MHz clock that runs 5ms at a time then stops (sends no data) to the screen for 5 ms. I am not sure if this would cause damage to the screen (I read that it the clock and syncs were not proper that damage could occur). I am wondering this because I have a pic that has an RTOS on it, and it would devote half of its time to updating the screen and the rest to the application.

I understand how to send the data over, and when to send what clock pulsed and sync pulses, but am not too sure about stopping the clocks.

Thanks in advance for your insight!

 

[ronsimpson]

Most TFT data sheets show a min and max clock rate. 13 to 16 mhz for example. 1mhz at 50% of the time will not work.
There is also a range for H and V sync.

 

[seasons555copy]

Ok thanks,
I wasn't sure because mine had a max of 16MHz but a dash for the min frequency.

 

[Noggin]

Driving an RGB interface using a PIC I'm sure is possible, and maybe fun, but I'd strongly suggest getting a graphic LCD driver IC. These IC's will have a much slower and simpler interface and have built in RAM to hold whatever is displayed on the screen. If you drive an LCD directly, you generally need to refresh the image on the screen continuously in my experience. If you have a 320x240 display, that takes about 230,400 bytes of RAM to hold all of the data that is shown on the display. Your PIC doesn't have that available so you'd need to use external RAM. Alternatively, you'd have a graphic driver chip with RAM built in, you send it the data as fast or as slow as you want, and it continuously sends the data to the LCD.

 

[seasons555copy]

The last time that I looked at the datasheet for this display was probably 6 months ago. I looked at it again today to remind myself why this question kept bothering me.
Here are the things that come to mind after looking at it.
1) The application circuit has a MCU driving the display instead of a display driver
2) It has a DE (data enable) input and the clock is labeled "Clock signal to sample each data". This is why I was wondering if I could stop sending it data for a period of time.
3) The clock has no minimum time, a max 0f 16MHz, and a typical of 9MHz.

I could not find the original data sheet for my display online, but this one is idential except for the model number.
https://www.displayfuture.com/engineering/specs/TFT/LTF430AS.pdf

Thanks again for all of your help so far.

 

[Noggin]

I don't know what would happen if you quit sending data. I had a few displays several years ago that would "forget" what was being shown if I didn't continuously feed it a pixel clock. It would just fade away. It took several seconds for it to happen so based on that I would say that you could send the data in spurts. However, that is a small sample size. I'd suggest using a graphics driver chip or a display with a chip built in.