Lpc2000

Thanks for the comment Glen,

I checked the timing with an Oscilloscope and it's fine.  The pulses stay 
for about 500nS (I'm using legacy GPIO mapping so it's slower).  A complete 
write cycle takes 940nS.  If anything I think it may be too slow, but I've 
seem this used with a 8051 (much slower) without any issues, unfortunately 
I don't have the source code for that.  Maybe I'll try using FGPIO and see 
if that makes a difference.

Does anyone know of any alternatives to SED13305 (that's cheap?)

Thanks!

-- Sean

At 07:15 2/16/2006, you wrote:
>Sean,
>
>I have used the SED 1335 in the past.  One thing that is too
>obvious is that the SED part is probably not the fastest thing
>in the world, and you may be exceeding it speed capability.
>
>I never had this problem with the Z80 family I was using at the
>time, but the new ARM chips are way too fast for the 1335, I do not
>know about the chip you are using.
>
>Just a thought.
>
>Glen
>
>
>Sean 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
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
>
>
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