Lpc2000

--- In lpc2000@yahoogroups.com, "tah2k" <tah2k@y...> wrote:
> > > I'm puzzled about the I/O:
> > > 1.) The IOPIN register does not necessarily reflect the state 
of 
> the 
> > > I/O line. For example, P0.4 is not connected on the Keil board. 
> > > Since this pin is configured as an input, I would suspect the 
> > > voltage on the pin to reflect the internal pullup, but it 
> measures 
> > > 0V. Even more puzzling, IOPIN0 states this input is high. Go 
> figure.
> > > 

Which pullup is that?  AFAIK, P0 pins do not have internal pullups - 
should not be left as unconnected inputs.

> > > 2.) Another concern: P0.31 is not connected, but configured as 
> an 
> > > input. If I measure the pin voltage it is 2.3 instead of 3.3V. 

Data Sheet says that P0.31 is output only.  I don't know what happens 
if you set it as an input in the IODIR register, but I guess you 
shouldn't do that.

Philips Apps: Description of IODIR register should probably note 
that, especially since current description says "Bit 31 in IO0DIR
controls P0.31"

> This 
> > > is also true for P1.16-23 and P1.24-25. Could I be leaking 
> current 
> > > through the pullup resistor?

What is input impedence of device you are using to measure?  Note 
that pull-up current is only 15uA minimum (equivalent to 220K @ 3.3V).


> > > 
> > > -Tim
> > ---  snip   -----