Timer A, time calculating?

Hi,

First, download the MSP430x2xx Family user's guide and read chapter 12 - Timer_A. If you select the ACLK (32768 Hz) as Timer_A clock source and then divide it by 8, you  will found the value that you need to put in the TACCR0 register.

Best regards,

AES

  Hi aes,

  I wrote here a part of my code. It suppose to work but it didn't. Where did i make mistake

  ....

  TACCTL0=CCIE;
  TACCR0=4096;
  TACTL=TASSEL_1+MC_1+ID_3;
  __bis_SR_register(LPM0_bits+GIE);

  ....

#pragma vector=TIMERA0_VECTOR

  ....

Hi ferhat,

   here is a simple solution use any TIMER A example in slac123 ,which uses auxiliary  clock i.e., 32768Hz  for ON/OFF ur led check with CRO how much time it is taking let it is 100 ms if u want some 10 secs  do a simple calculation ( 10 secs/100 ms= 100) make a use a flag and inside the timer interrupt loop increment it and wait for 100 if it reaches 100 make the led glow and clear the flag.

a Very simple solution am i right??

Regards

Kshatriya

Aes, i tried your code but it didn't work. Why did you use TACCR0's value 61440 and LPM3? I want to learn how can we calculate TACCR0 for different time intervals?

Kshatriya, how can i check my led with CR0 how much time it is taking?

Thanks.

Hi,

I tested the code in a MSP430FG4618/F2013 Experimenter Board. If you are using IAR please check if the FET option is selected (not in simulation mode).

The TACCR0 value is computed as follow:

1-     TIMER A input clock is 32768 Hz. This clock is dived by 8, TIMER A frequency will be 4096 Hz.

2-     Each TIMER tick count 1/4096 sec.

3-     If you need 15 sec this will be equivalent to 4096*15 = 61440 tick counts.

Regards,

AES

Hi, connect ur CRO GND pin to ur board GND pin, and the touch the other probe with ur LED pin where u connect with the controller, or simply touch with the controller pin which pin u connected with controller.

follow AES suggestions for to get  proper count value,  i think u didn't get any count value for a delay of 15 secs so make a maximum delay of 1 sec. and do the procedures what i said in previous post.

Regards

Khatriya

Thanks for help.

Regards.

AES said:

Hi,

 

Try this

//******************************************************************************
#include <msp430xG46x.h>
//******************************************************************************
//TIMER_A interrupt service routine - (CCRO)
//******************************************************************************
#pragma vector = TIMERA0_VECTOR
__interrupt void TIMER_A (void)
{
  P2OUT ^= 0x02;
  //TACCTL0 &= 0xfffe;                           // clean interrrupt flag
}
//******************************************************************************
// main code
//******************************************************************************
void main (void)
{
  WDTCTL = WDTPW + WDTHOLD;                  // wd stop
 
  P2SEL = 0x00;                              // config P2 to I/O
  P2DIR = 0x02;                              // config P2.1 output
   
  TACCTL0 = CCIE;                             // TACCRO interrupt enable
  TACCR0 = 61440;                            // counting time CCR0
  TACTL = TASSEL_1 + ID_3 + MC_1;            // TIMER_A
 
  _BIS_SR (LPM3_bits + GIE);                    //LPM3 with GIE 
}

 

 

 

 

 

Hi AES!

What if we use this code to show texts for a period of time? I don't know why the Timer A function is not called in the main?!!!