Hello,
We are using the DS90UB949 on our own PCB to talk to a DS90UB948 inside a customer screen module. While the display works fine most of the time, we sometimes get a series of vertical lines appearing across the screen. These lines appear to be spaced every other pixel and the pattern spans the entire width of the screen. We've been attempting to debug to no avail, but here's what we have found out:
1. The vertical lines can be triggered in multiple ways: resetting the screen module, resetting the 949, setting the HDMI Digital Reset bit, unplugging the HDMI cable and plugging it back in.
2. The DUAL_STS register (0x5A) in the 949 reads as 0xCD (the expected value), indicating that the problem doesn't seem to involve the deserializer link or the HDMI clock frequency.
3. When the Pattern Generator is enabled using the External Clock while the vertical lines are on the screen, they remain there for any pattern selected. However, if the Pattern Generator is set up to use the Internal Clock, the lines never appear on the screen - even if they were previously there on the HDMI signal.
This all points to there being some kind of problem with the HDMI clock, but none of the status registers I've read so far show any issues detecting it. The HDMI frequency is reading as 156 MHz, which is expected for the 1920x1200 resolution we're dealing with.
Please let me know if there is any additional information I can provide to help resolve this issue.
Thanks,
Josh