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ADV7611 - 720p in BT.656 mode?

Question asked by pajko on Dec 20, 2012
Latest reply on Dec 20, 2012 by GuenterL

Does the ADV7611 support 720p in BT.656 mode? I've found some conflict in the documentation, and after reading through some related threads, I got more confused.


1) The datasheet does not mention anything about 720p, but contains the following:

"Modes 0x00 and 0x0A require additional writes to IO Map Register 0x19[7:6] = 2’b11 and IO Map Register 0x33[6] = 1"

This register configuration sets up clock doubling on the pixel bus. Why is this necessary?


2) UG-180 contains a guide on page 27 about how to set up 720p in BT.656 mode:

"The Table 8 and Table 9 show the settings that must be used to enable 8-/10-/12-bit, 656 output. Note that 720p 8-/10-/12-bit mode must

use OP_FORMAT_SEL=0x20 or 0x2A (refer to Table 73). Doubling the clock as per Table 8 undoes the DDR mode. "

Here the clock doubling is clearly described (the settings are the same as above), I understand it's necessity, and the background behind it. Based on this the 720p should be supported, however:


3) The datasheet mentions a pixel clock restriction in DDR mode:

"DDR mode is only supported only up to 50 MHz (an equivalent to data rate clocked 100 MHz clock in SDR mode)."

Does this limitation apply for 720p resolution, where the pixel output is basically SDR with double pixel clock (being 148.5 MHz, which still meets the range supported by ADV7611)? Or does it only apply for situations, where the pixel output is really DDR?


4) If the ADV7611 does not support 720p in BT.656 mode, then does Analog manufacture some component, which supports it? Unfortunately the BT.656(-like) input is a restriction of the CPU, which we will have to live with. I found out ADV7619 could be a candidate, but it's documentation contains all the things mentioned above, although the restriction mentioned in 3) is a bit more informative, but does not help anything in my confusion:

"DDR can be supported with LLC clock frequency up to 50 MHz (video modes with original pixel clock lower than 100 MHz, such as 1080i60)"


Thanks for any help.