Lpc2000

At 02:34 PM 5/3/05 +0000, roger_lynx wrote:
>--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> wrote:
> > At 12:15 PM 5/3/05 +0000, roger_lynx wrote:
> > >I found this explanation, in 2131_UM, pg. 88:
> > >
>
>[edited]
>
> > >and P0.[7:0] and at the same time set P0.[15:8] to 0xA5,
> > >regardless of the previous value of pins P0.[15:8]:
> > >
> > >IO0PIN = (IO0PIN && #0xFFFF00FF) || #0x0000A500
> >
> > Ignoring the # as a typo.
>
>Yes, typo, but it is a *logical* AND and OR, as the original text
>emphasizes, as well.

Somehow I missed the logical operation part.  I must have been blinded by 
the # :).  I can't imagine a circumstance in which that would work.

>
> > That code depends on IO0PIN containing the last result written to
>it.  I
> > don't remember that being documented as the case.  I certainly would
>not
> > trust it.
>
>I do not either, the result is 1 or 0, no?

The result is always 1, any nonzero value logically ored with another value 
will result in a 1 by definition in C or C++.



> > >I got 3.4+ MHz pin state change rate, I need now fraction of it, yet I
> > >cannot get it.
> > >VPBDIV=1.
> >
> > I'm afraid that's it.  I suspect that the update rate using IOPIN
>could be > faster but you do have the overhead of a shadow register to
> > consider.  Certainly as far as IOSET/CLR are concerned you've hit
>the > limit.  Also note if you use the code example above for IOPIN
>control I
> > would not expect a speed increase since it has two access's to IOPIN.
>
>I am concerned about the missing bit updates.
>The speed is okay.
>See section "photos", I just uploaded the outcome of that missing bit
>update - the text is "rough on edges".

The only problems I'm aware of with IOSET/CLR are
  - phasing, inherit with this method
  - speed, not an issue for me but some people want to do fast bit banging 
through the ports.
  - IIC pins (those that can be mapped to be IIC) do not pull up even when 
set high even when not used as IIC.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/