Unable to get the timer working correctly in LPC2148

I  have written code for delay using timer in LPC2148. But I am not able
to get the desired time delay. 1 Sec delay if I give, it looks like 100
msec (Ddd not calculate correctly). Somewhere something is wrong it
looks. Anybody can help? I have written code comments and I hope it is
good enough. Also is it good idea to disable and enable timer as in
delayus() or allow timer to run continuously instead reset the T0TC?
Which one is efficient? I felt clearing T0TC might be efficient since it
takes only one instruction cycle.

// Timer resolution is 10 micro  Second with PCLK = 15 MHz.


void initTimer0(void)
{
    /*PLL0 has been setup with CCLK = 60Mhz and PCLK  = 15Mhz.*/
   // 150 count @15 MHz means 10 usec. So TC gets incremented every 10
usec
    T0CTCR = 0x0;       // Select the timer mode. 
    T0PR = 150-1; //(Value in Decimal!) - Increment T0TC at every 150
clock cycles
                     //Count begins from zero hence subtracting 1


    T0TCR = 0x02; //Reset Timer
}



 // Function below is used to give a delay in micro seconds.
 // Delay in 10 usec multiples is possible
void delayus(unsigned int microSecond) //Using Timer0
{
    // In case the value is not multiple of 10, make it multile of 10 by
adding the difference
    if((microSecond % 10)!=0)
    {
        microSecond = microSecond + (10-microSecond%10);
    }

    T0TCR = 0x02; //Reset Timer

    T0TCR = 0x01; //Enable timer
    // Reset the Timer counter

//  T0TC=0;                // Need not reset since we are disabling the
timer itself and then enabling
                            // Probably we need not disable timer,
instead we could reset this TOTC.

    while(T0TC < (microSecond/10)); //PR is loaded such that TC updates
every 10 microsecond.
                                    // So the T0TC count value required
= microsecond/10


    T0TCR = 0x00; //Disable timer
}

// The following function gives delay in milliseconds. 
void delayMS(unsigned int milliseconds) //Using Timer0
{
   delayus( milliseconds*1000);
}


---------------------------------------
Posted through http://www.EmbeddedRelated.com

Am 07.04.2015 um 13:34 schrieb shankariamma:
> I  have written code for delay using timer in LPC2148. But I am not able
> to get the desired time delay. 1 Sec delay if I give, it looks like 100
> msec (Ddd not calculate correctly).

What do you mean "looks like"?  How about you sit down and make an 
actual _measurement_ of your delay?

> I have written code comments and I hope it is
> good enough. Also is it good idea to disable and enable timer as in
> delayus() or allow timer to run continuously instead reset the T0TC?

In the majority of situations, you need neither.  You can just leave the 
timer running in the background.

> // Timer resolution is 10 micro Second

How many ticks of that size are in one whole second?  Are you sure the 
time can really count all that far?

Have you even tried any delays shorter than 1 second?  E.g. is there a 
difference between a single delayms(1000) and, say, 10 calls of 
delayms(100), or 100 calls of delayms(10)?

And what exactly, do you think, will the rest of your hardware think of 
your CPU doing _nothing_at_all_, for an entire second?  Might there be, 
dunno, a "watchdog" out there that would forbid such things?

>   // Function below is used to give a delay in micro seconds.
>   // Delay in 10 usec multiples is possible
> void delayus(unsigned int microSecond) //Using Timer0
> {
>      // In case the value is not multiple of 10, make it multile of 10 by
> adding the difference
>      if((microSecond % 10)!=0)
>      {
>          microSecond = microSecond + (10-microSecond%10);
>      }

The above is quite a complete waste of effort.

> //  T0TC=0;                // Need not reset since we are disabling the
> timer itself and then enabling

Sure that's actually true, i.e. that the timer doesn't retain its 
previous value and starts from there?

Hello,
Appreciate your time in going through the code. I am new to Embedded
Programming. It would be good if you give suggestions as well in
addition to asking only questions. If I am expert programmer, why should
I ask these simple questions?
I want 10 usec or 100 usec resolution. But not able to get this done.
---------------------------------------
Posted through http://www.EmbeddedRelated.com

On 08/04/15 06:57, shankariamma wrote:
> Hello,
> Appreciate your time in going through the code. I am new to Embedded
> Programming. It would be good if you give suggestions as well in
> addition to asking only questions. If I am expert programmer, why should
> I ask these simple questions?
> I want 10 usec or 100 usec resolution. But not able to get this done.
> ---------------------------------------
> Posted through http://www.EmbeddedRelated.com
> 

No one is going to write your code for you (unless you hire them as a
consultant, of course).  This is especially true when you are a beginner
- it is important that you /learn/ what you are doing, not just copy it
from someone else without understanding.  That is why Hans-Bernhard took
the time to ask you important questions, designed to make you think
about the code and perhaps fix things yourself.

I can give you one further suggestion - assuming your timer is 32-bit
(/you/ will have to check this), run it at 1 MHz to count microseconds.
 Then you can drop all the messy and inefficient divide by 10 code.  I
recommend you also calculate the limit time of any counter, to be sure
that it can handle any delay you might need - post your answer here and
we can confirm it for you.

Also, if you are going to use Usenet, please get yourself a proper
newsreader and newsserver instead of the crappy "EmbeddedRelated"
interface.  Then you can post properly, including quoting.  For many
people, Thunderbird is a fine choice of newsreader - it is easy to use,
free, and works on all platforms.  www.eternal-september.org is a free
newsserver that is very popular, as many ISP's no longer provide a
Usenet server.  A proper Usenet setup will make it easier for you to ask
questions, and easier for others to answer you.

mvh.,

David

On 08/04/15 05:57, shankariamma wrote:
> If I am expert programmer, why should
> I ask these simple questions?

http://www.catb.org/esr/faqs/smart-questions.html