Lpc2000

Again, proof that this group is on the cutting edge of LPC2100 
development.  ;-)  The VPBDIV read problem is official, official 
philips description:

The problem of read of VPBDIV register is confirmed: read of VPBDIV 
register may return a wrong  value. The workaround is to read the 
VPBDIV register twice consecutively and the second read always 
returns the correct value. The write to VPBDIV, the function of 
VPBDIV and the other VPB/AHB registers are not affected.

Richard

--- In lpc2100@yahoogroups.com, "jvedum" <j.vedum@o...> wrote:
> Yes, I have also had problems reading the VPB registers. Sometimes 
I 
> need to read more than twice. But writin the register seems to work 
> without problems.
> 
> Jon Vedum
> 
> 
> --- In lpc2100@yahoogroups.com, Robert Adsett <subscriptions@a...> 
> wrote:
> > I'm seeing some odd behaviour in the VPB registers that I haven't 
> been able 
> > to track down so far.  So I thought I would check to see if 
anyone 
> else had 
> > run across it yet.  The following is a code fragment I'm using to 
> read the 
> > VPB divider so that I can determine the clock speed the 
peripherals 
> see.
> > 
> >   *ptr = (VPB_param)VPBDIV;/*lint !e930*/
> >   switch( VPBDIV & 0x3) {
> >      case VPB_DIV_ONE:
> >           *ptr =  VPB_DIV1;
> >           break;
> > 
> >      case VPB_DIV_HALF:
> >           *ptr =  VPB_DIV2;
> >           break;
> > 
> >      case VPB_DIV_QUARTER:
> >           *ptr =  VPB_DIV4;
> >           break;
> > 
> >      default:
> >           r->_errno = EINVAL;
> >           return -1;
> >      }
> >   return 0;
> > 
> > Notice that I'm reading the divider twice.  The first time is 
just 
> thrown 
> > away.  If I remove that first read and just use the one in the 
> switch I get 
> > an incorrect result.  The assembly output does appear to be 
correct.
> > 
> > Anyone seen anything like this before?  I don't have a nice short 
> > reproducible test case yet.  For now I'm living with the 
workaround 
> but I'm 
> > worried about what else may be lurking out there.
> > 
> > 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