• State Not Answered
  • Locked Locked
  • Replies 31 replies
  • Subscribers 15 subscribers
  • Views 7885 views
  • Users 0 members are here
Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Problem with delay timing with LPC2148

kaushik ghosh

Hi guys...I'm a newbie in ARM7 programming.I have a readymade hardware board of LPC2148.I'm doing a simple blinking action on it.I'm supplying the processor with 12MHz frequency as its processor clock.And i hve read in net somewhere tht each for loop [for(x=0;x<1;x++)] takes 12-13 cycles to execute.So by rough calculation the value of the delay counter should be 1000000 for 1sec delay.But my delay turns out to be 4-5sec.
I have deactivated the MAM block and also PLL0 i.e., I'm using the external supplied oscillator as the clock source for the processor.
I havn't used the timer module to get the desired delay till now..as i need to brush up the theories behind it first.But whether it is absolutely necessary to use the timer block to produce the 1sec delay?? plz answer my post some one..thanks in advance.My code is given below --

#include "LPC214x.H"

   /*   Fosc = external supplied crystal frequency
                Fcclk = Processor clock or o/p of PLL0
                Pclk =  The VPB clock frquency.The o/p of the VPB driver
                Fcco = the frequency of the PLL current controlled oscillator */
void init_clock()
{
/*      PLL0CON = 0x03;         // PLL0 is enabled & connected as the clock source of the microcontroller
        PLL0CFG = 0x24;         // The i/p crystal oscillator frequency is multiplied in the PLL0 block by a fator of 5(=4+1)
        PLL0FEED == 0xAA;       // 0xAA and 0x55 should be feed into this register for the
        PLL0FEED == 0x55;       // changes in PLL0CON and PLL0CFG to take place actively
        VPBDIV  = 0x01;         // The Pclk frequency = Fcclk frequecy..not necessary.
                                                // by default the GPIO are selacted as legacy ports
*/
        PLL0CON=0x0;              // these 4 lins are as given by blink.c.Though the result is nt coming as expected.the above commented out result are my first try to supply the processor with 60MHz clock supply
                                                  // the PLL is nt connected as the clock source for the processor
        PLL0FEED=0xAA;
        PLL0FEED=0x55;
        VPBDIV=0x00;
        MAMCR = 0x00;           // Any MAM function is disabled..i.e
}

void delay()
{
        unsigned long int i;
        for(i=0;i<250000;i++);

}  // with 12MHZ clock supply the time delay is cmng as 1sec if the delay value is 250000 but it should be 1000000 according to my calculation
// in this

void main(void)
{
        unsigned long dword=0x00000000;
        unsigned char min_hand=0;
        init_clock();
        PINSEL1 &= 0x00000000; // all the pins of port1 are selected as GPIO
        IODIR1 = 0x00FF0000;   // the pin 16 to 23 are configuered as the o/p pins.
        IOCLR1 =  0xFFFFFFFF;
        while(1)
        {
                min_hand++;
                dword = dword>>16;
                dword++;
                dword = dword <<16;
                IOSET1 |=  dword;
//              IOPIN1 =  IOSET1;
                delay();
                if(min_hand /60 == 0)
                {
                        min_hand=0;
                        delay();
                }
                IOCLR1 =  0xFFFFFFFF;
                delay();
        }

}