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Hey everyone I am looking into VGA protocol. I have researched a lot but only thing I could not figure out is this:

Does VGA vertical sync and horizontal sync needs to be sent over and over to keep the image on the display?

Or do you need to send these signals to just change the image on the screen?

So if i send my image to screen once do I need to clock the same image to the screen to keep the image?

Thanks.

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VGA isn't a protocol that is talked to some memory. The intensity values are used directly to modulate the intensity of an electron beam hitting the fosphor in your screen. So yes, you need all these signals to keep the electron beam travelling to the right places in your CRT. LCD monitors that have an VGA input are just emulating that behaviour, so yes, they will need all that too.

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Vertical and horizontal synch needs to be sent all the time.

The monitor uses the vertical synch to synchronize the top of the picture to the top of the screen. It uses the horizontal synch to ensure that each line starts at the left hand side of the screen.

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VGA display was created when we have CRT monitors. They did not have a frame memory. Even though we can have frame memory now, that is not how display monitors work. Unlike a small LCD which is often used to show static images like menus or logos, a display monitor shows a sequence of images i.e a video. Therefore, even if the image has not changed since last frame, we still need to send data to it. Thus you will need to send the sync signals anyway.

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