Lpc2000

Yes, I have issued the init properly, however I don't know if the chip is 
receiving the commands correctly.  Either way I don't think that you need 
full init to get access to video ram (other than setting the 
pages).  Before every read or write command I send the Set Cursor command, 
so that's fine.  Since enough reads will show that every byte was set 
successfully I think the problem is on read, not write, but then this 
doesn't explain why I'm not seeing anything displayed on the screen at 
all.  I still haven't figured out what is going on yet.

I just don't understand how changing the WRITE sequence can cause repeated 
READs to return varying data.  The only thing I can think of is there must 
be some voltage issues somewhere.  When I try running the SED chip off of 
5V I just get garbage on every read, which is pretty strange.  The VRAM I'm 
currently using requires 5V, but regardless if I power it off of 3.3V or 5V 
I get the same response, leading me to think that the VRAM isn't the 
issue.  However I don't understand why the system doesn't work when I try 
running it off of 5V.

Anyway thanks for the suggestions.  I may have to go back to the drawing 
board on this one.

-- Sean

At 14:29 2/18/2006, you wrote:
>Hi Sean,
>do you make a proper initialization of S1D13305?
>I mean before to write to the memory. Have you issue
>commands SystemSet, ScrollToAddress and etc. with
>proper parameters?
>
>
>
>--- Sean <embeddedrelated@...> wrote:
>
> > Hello all,
> >
> > I am having an issue here and I hope someone has
> > some suggestions.  I'm
> > trying to interface some LCDs to my micro, I have a
> > graphical 128x64 which
> > has an embedded controller chip interfaced fine,
> > using P1.16-P1.23 as 8-bit
> > parallel IO.  However when I try to hook up a
> > SED13305 the data seems to
> > get corrupted.  I'll issue a write to the device to
> > store something in
> > VRAM, then immediately try to read it back.  Here's
> > where things get weird.
> >
> > If I try to use the WR and RD signals like they
> > should be used (RD always
> > high, Clear WR, Set Byte, Set WR), the write appears
> > to work, however
> > repeated reads of the same memory area return
> > different results each
> > time.  Enough reads show that the data was written
> > successfully.  However
> > if I modify only the write routine to use the WR and
> > RD signals in a
> > different (wrong) way (Clear WR, Set RD, Set Byte,
> > Set WR, Clear RD) then
> > repeated reads return the same data every time,
> > however bits 7:8 are always
> > "10".  Note that the read routine is the exact same
> > both times.
> >
> > How is it possible to have a small change to the
> > write routine effect how
> > the read routine works?
> >
> > I have tried playing with timing to no avail.  I
> > looked at everything with
> > an oscilloscope and the timing and data look
> > correct.  I've verified all
> > connections with a multimeter. I have both the micro
> > and the SED running
> > off of 3.3V.  Note that if the SED is running at 5V
> > then I get complete
> > garbage on read (meaning probably nothing worked),
> > even though the SED says
> > it works from 2.7V to 5.5V.
> >
> > I think I'm going to have to try to make another
> > test board, but before I
> > run out to do that does anyone have any ideas as to
> > why this is happening?
> >
> > Thanks,
> >
> > -- Sean
> >
> >
>
>
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