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.