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EPPI window regs (output mode)

Question asked by RichardJ on Aug 26, 2011
Latest reply on Sep 1, 2011 by RichardJ

Apologies to those who've already seen my cry for help on this subject. I tagged it onto one of my earlier posts but the title didn't mention "Window regs", the point of this post.


I've a 1920x1080 x 25fps picture on my HD TV from a BF547 with an AD9889 HDMI driver on it's EPPI.

I really want to display 1440x810 pixels so I thought I tried setting the window registers and DMA accordingly:


With the EPPI set up to scan 1920x1080 in the following cases:


  • Window regs set to   H_COUNT=1920 by V_COUNT=1080

DMA13                    X_COUNT=480    by Y_COUNT=1080   rows I get the full screen (480x32-bit words -> 1920x8-bit  pixels)


  • Window regs set to   HCOUNT =1440   by V_COUNT=810

DMA13                    X_COUNT=360   by Y_COUNT=810    rows I get scrolling/rolling zig-zags (360x32-bit words -> 1440x8-bit pixels)



While I experimented I found something that to me suggests the window regs don't work as expected in output mode:


  • Window regs set to   H_COUNT=1920 by Y_COUNT=500

DMA13                     X_COUNT=480   by Y_COUNT=1080 rows


I expected to get rubbish as the DMA would overflow onto the next frame and so on. Well I don't, I still have a full screen displayed, all 1080 lines. It's not taking any notice of VCOUNT.