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(ADV7511) Outputting at 640x480

Question asked by aaron.elec on Dec 21, 2016
Latest reply on Dec 22, 2016 by aaron.elec

Hi, I am wondering if there are any special tricks that the ADV7511 requires in order to output at 640x480 at either 30 or 60 Hz. Please note that I have written an HDMI driver for 1080p60 using the ADV7511, and it is fully functional, however, when I change all the necessary values to output 640x480, there is no signal on the monitor. 

 

Some details:

I am using seperate hsync/vsync, and using generated DE. For the chip to generate DE at different resolutions, I am aware that registers 0x35,0x36,0x37,0x38,0x39,0x3A need to have the recommended values for 480p instead of 1080p. I changed these as was suggested in the ADV7511 Programming Guide, table 33, p56.

The VGA timing specifications I am using are these:

ModeMHznsH VisibleH FrontH SyncH BackH WholeHSyncV VisableV FrontV SyncV BackV WholeVsync
640x480x6025.17539.72640169648800-48010233525-

The pixel clock I am supplying is very close to 25.806 Mhz.

Seperate Vsync = ~62 Hz

Seperate Hsync = ~33.25 kHz 

The monitor I am using has the following scan specs:

Model U2415

Horizontal scan range 30 kHz to 83 kHz (automatic)

Vertical scan range 56 Hz to 76 Hz (automatic)

So I believe I am in spec here. The monitor user guide also specifically states that there is 480p support.

 

So what I am asking here is that is there something I have neglected that must be done for 640x480 that is not necessary for 1080p? Are there any register values that need to be changed to enable this?

 

Thanks for your time

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