Re: [uCsimm] LCD weirdness

From: David Williams (
Date: Sun Mar 26 2000 - 17:08:26 EST

Another thought!

Have a look at the contents of the memory being used as the display memory. Perhaps
it does not contain what you think! If it is correct then you could trigger a CRO
from the LFLM signal and look at the data imediately after this pulse to see what is
being output by the LCD controller. If is OK then you are in trouble. If not OK then
look at the display memory. If all electricals are OK then suspect a programming
problem. Are chip selects set up correctly for memory being used for display memory?
Is LCD controller DMA setup correctly? Is display memory simply being corrupted?

Good Luck

David Williams wrote:

> Hmm...
> Sounds like a timing problem to me. I would be looking at what happens
> near LFLM transitions. I have used a custom LCD display interfaced to
> 68EZ328 without problem.
> Dave.
> Tom Walsh wrote:
> > Has anyone experienced unexpected inverse video when using a 1/4
> > (Sharp LM32019) or full vga (Epson EG9013) LCD displays? I have yet
> > to put a 'scope onto the data lines, but it is related to the value of
> > the first byte of the first line at the start of a frame. If this
> > byte is set to 0xff, then the bitstream for that frame will be
> > reversed, else if the the byte is 0x00, the bitstream is displayed as
> > expected (normal video). No other byte value at any other location
> > within the display memory has this effect, only the first byte pumped
> > out at the beginning the Frame has this effect.
> >
> >
> > Is this an "undocumented feature"?
> >
> >
> > TomW
> >
> >
> > --
> > Tom Walsh - WN3L - Embedded Systems Consultant
> > '', ''
> > "Windows? No thanks, I have work to do..."
> >
> >
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