Lpc2000

Thanks for your results

What lpc are you using by the way? Is your RTC counting at the right 
speed when VPBDIV=0? Try comparing the RTC timers against a normal 
clock if u can.

I tried your code on my 12 MHz board (M=5), and this is what I get.
VPBDIV = 0 so VPB = 15MHz (cclk/4)
PREINT = 0x000001c8;
PREFRAC = 0x000061c0;
RTC runs OK, but it's going twice as fast.
....
VPBDIV = 1 then  VPB = 60MHz (cclk)
PREINT = 0x00000726;
PREFRAC = 0x00000700;
RTC runs OK. Speed is normal.
....
VPBDIV = 2 then  VPB = 30MHz (cclk/2)
PREINT = 0x00000392;
PREFRAC = 0x00004380;
RTC runs OK. Speed is normal.

For now, It's still unsolved over here.

Thanks,
Leighton

I've included pieces of my code just for reference.
************************************
#define XTAL_FREQ     12000000
//#define XTAL_FREQ     14745600
#define MULTIPLIER    5
//#define MULTIPLIER    4
#define CCLK          (XTAL_FREQ * MULTIPLIER)      // system clock 
system clock (cclk)
#define PCLK          (CCLK / 2)
//#define PCLK          CCLK
//#define PCLK          (CCLK / 4)

if(PCLK == CCLK)
{ 
  VPBDIV = 1;
}
else if(PCLK == CCLK/2)
{ 
  VPBDIV = 2;
}
else if(PCLK == CCLK/4)
{ 
  VPBDIV = 0;
}

CCR = AMR = CIIR = ILR = 0;   //clear all RTC Misc registers
SEC = MIN = HOUR = 0;       //clear timer registers being used

//Setup Prescalar Values
PREINT = (PCLK/32768) - 1;               //integer value
PREFRAC =PCLK - ((PREINT + 1)* 32768);   //fraction value

CCR |= 2;                         //reset timer
CCR &= ~2;
CCR |= 1;                        //start timer




--- In lpc2000@yahoogroups.com, "Pete" <peterbrown_abroad@y...> 
wrote:
> 
> 
> ok, got home and have tried on my dev board...
> Using a 12Mhz crystal, I configured the VPBDiv=0
> 
> As a result modified the Fac and Int settings to:
> PREINT 		= 0x000001c8;//Set RTC prescaler for 
12.000Mhz Xtal,
> 	VBP=15Mhz
> PREFRAC 	= 0x000061c0;
> 
> using the calculations from databook.
> 
> I also then had to change my UART settings to match, sicne the 
PCLK 
> was now 1/4.....
> Anyway: ALL WORKS OK. RTC functions normally.
> 
> Can you check what values you used for the Prefac/int when you 
> adjusted the VPBDiv?
> 
> Or, since you have it working maybe issue is closed?
> 
> anyway, thought i would report my findings!
> 
> rgds
> pete
> 
> 
> So I am confused that you say you had problem with the 
> 
> --- In lpc2000@yahoogroups.com, "bty639886" <peter.brown@b...> 
wrote:
> > 
> > when i get home i will check this out on my systsem.
> > 
> > I do however have a 12Mhz clock rather than the 14.xx that u are 
> > using. So my preints and facs will be different.
> > Im suspecting the problem could well be with your prefac being 0 
> > given the divider settings...
> > 
> > anyway, i will check it out and re-post for future reference.
> > 
> > glad you got it working !
> > rgds
> > pete
> > 
> > 
> > --- In lpc2000@yahoogroups.com, "Leighton Rowe" 
> <leightonsrowe@y...> 
> > wrote:
> > > 
> > > > 3. have you tried running with vpbdiv set to 1 (ie resulting 
> in 
> > > > 60mhz opertion (ish).. i am using that for my system without 
> any 
> > > > problem...
> > > 
> > > Good news!
> > > 
> > > After setting VPBDIV = 1 (pclk =cclk) and setting PREINT and 
> > PREFRAC 
> > > (based on the user manual), the RTC counted correctly. Thanks 
> > Pete. 
> > > The RTC also worked for VPBDIV = 2 (pclk = cclk/2).
> > > 
> > > But interestingly, the RTC still counted twice as fast after 
> using 
> > > VPBDIV = 0. I repeated everything on 2 different lpcs (lpc2114 
> > > @14.7456MHz & lpc2129 @12MHz). You can even try it out on your 
> > own; 
> > > I wouldn't be surprised you'll get the same results. and got 
the 
> > > same results. 
> > > 
> > > So RTC's OK only when vpbdiv = 1 (pclk=cclk) or 2 (pclk = 
> cclk/2). 
> > > Otherwise RTC's doubles in speed when vpbdiv = 0 (cclk/4). I 
> hope 
> > > Philips has an explanation for this one...I have no clue why. 
> > > 
> > > For now, I can live with using a different vpbdiv setting to 
> make 
> > > everything work. 
> > > 
> > > Thanks again