Lpc2000

Thanks Richard.

I think I discovered 99% of the problem.  Apparently, I was shipped
samples of the Serial RAM FM24C256 chip that were true 5V parts and I
asked for 3.3V.  Makes it a little difficult to get the chip to work
:)  But, I will also change my pullups when I get the correct chip in.
 They are too high.  

I've been a software designer for many years and I am trying to learn
more about the hardware side and do some of the design myself.  I
found I don't learn how the hardware works as well if I have someone
else do all the hardware design.  So, sometimes I miss some things in
the datasheet that are very important (4.7K pullups instead of 10K). 
It's fun to learn, though.

Sutton



--- In lpc2000@yahoogroups.com, "rtstofer" <rstofer@...> wrote:
>
> --- In lpc2000@yahoogroups.com, "Sutton Mehaffey" <sutton@> wrote:
> >
> > Charles,
> > 
> > Using 10K pullups.
> > 
> 
> 10k isn't a pull-up when applied to I2C.  The absolute maximum that
> might work on a good day is about 4.7k and a more realistic value is
2.2k.
> 
> You never provided a link to the RAM device (that I recall) but in
> looking at the FM24CL64, they recommend a 1.1k pull-up.  The reason it
> is so small is the lower VDD.  Normally, at 5V VDD the pull-up can go
> as low as 2k, maybe 1.8k.  At 3.3V the resistor would be somewhat
smaller.
> 
> But, again, I don't know which device you are using.
> 
> Richard
>