Blanking in displays

[FreshmanNewbie]

In this AppNote, https://www.ti.com/lit/ta/sszt622/s...98103&ref_url=https%3A%2F%2Fwww.google.com%2F,

in the first page itself, they mention, "Blanking", but I do not understand why this blanking factor should be included in the calculation of Pixel clock or data rate?

Can someone explain to me?

 

[KlausST]

Hi,

let´s say a football game consists of two halfes 45 min each and a break of 15 min.

How much minutes pass from beginning to end?
Hint: On a watch the minutes still count in the break, even if the players are not on the field.
So it´s not 2x45 = 90 min, but it´s 105 min.

--> The clock does not stop counting during the break.
or : the pixel clock does not stop during blanking.

Klaus

 

[barry]

Hi,

let´s say a football game consists of two halfes 45 min each and a break of 15 min.

How much minutes pass from beginning to end?
Hint: On a watch the minutes still count in the break, even if the players are not on the field.
So it´s not 2x45 = 90 min, but it´s 105 min.

--> The clock does not stop counting during the break.
or : the pixel clock does not stop during blanking.

Klaus

Is that American football or rest-of-the-world football?

 

[Externet]

Only the real foot ball plays in two 45 minutes halves.

 

[betwixt]

I'm not a sports follower so I will attempt to answer the original question. Anyway, my country isn't doing very well at the moment

The display controller notes appears to be for computer or TV LCD display. Part of the display is visible but there will usually be some "off the borders" that has no image in it. The invisible area still needs the clock running but shouldn't have pixels data, it's called the blanking period. In the case of a TV display, that period might carry caption data, screen format information and synchronizing signals to ensure each line (row of pixels) and frame (top to bottom) starts at the correct time. On a computer application, the blanking period may be used to update the display memory so each frame starts with a new image instead of it updating while you can see it. Behind every pixel there is a block, possibly several bytes long, of memory that holds the red, green and blue brightness for that pixel, the display controller would constantly read that memory and "map" it to the display. It is done that way so the image stays present if the LCD isn't fed new information, it just keeps repeating what it has already got in memory. The blanking period allows the computer to update the memory and therefore the image in one operation so the image is the new one from start of scan. If you don't do that, the display would flicker as the memory would be written to and read at the same time.

Its really a lot more technical than that but I hope that gives some insight.