Tiva C Timer

Thank you for suggestions but for 1st stage i want to calculate time.can you tell me a simpler & precise way of doing it

Hi,

About your words: …want to calculate time… if you mean by that summing up execution time for each instruction - you may use the simulator for that, but best is to measure because measurement takes into account the flash access time which cannot be predicted by you - so the measurement in cycle time is below:

Insert in your file (at right places):

#include "inc/hw_nvic.h"

#include "inc/hw_memmap.h"

#define DWT_O_CYCCNT 0x00000004

static        uint32_t                  c_start, c_stop;

void EnableTiming(void){

static int enabled = 0;

if (!enabled){

   HWREG(NVIC_DBG_INT) |= 0x01000000;            /*enable TRCENA bit in NVIC_DBG_INT*/

   HWREG(DWT_BASE + DWT_O_CYCCNT) = 0;   /* reset the counter */

   HWREG(DWT_BASE) |= 0x01;                                 /* enable the counter */

   enabled = 1;

 }

}

and then, in the code to be examined write these, after a call of EnableTimig():

 c_start = HWREG(DWT_BASE + DWT_O_CYCCNT); // at the beginning of the code

 // your code follows here

 c_stop = HWREG(DWT_BASE + DWT_O_CYCCNT); // at the end of the code

then c_stop - c_start is the execution number of cycles for the code; just multiply with clock period to find out the execution time of the code.

Petrei

This is what i am Getting....The compiler is showing that the expression must have a modifiable lvalue

Hi,

I cannot see all yours #includes - please add this if not already added:

#include "inc/hw_types.h"       /* for definition of HWREG */

Petrei

when i run the code initially the value of c_start & c_stop is 0 & after execution the value of c_start is 17 & c_stop is 0 & my program is taking around 1 minute to execute.is these value that i am getting is correct?? & what should i do to calculate time & are these 17 clock cycles??

Hi,

First, depends when you started and when you stopped. But you must take into account other aspects: that register (dbg) is 32 bits long, so 2^32 times the clock period will give you a maximum length of correct measurements, which can be in the range of seconds, depends on your settings.

If this is the case, then this ultra precise measurement should be avoided and replace by the system timer set at one or ten milliseconds. Take care how you start it and stop it.

Another approach can be to measure small portions of your code, the most important ones. Choose whatever is convenient to you.

Petrei

Hii,

Thanx for the reply..I want to use the timer option with 1 millisecond.I want that a variable or timer initialized at 0 in the beginning should show me the total no of clock cycles or time of exectuion of complete program at the end.can you help me in programming that?..can we use inbuilt timers to calculate these? If yes then how to program them?

hii,

I had set the breakpoint at wrong position.this this i had set the breakpoint on return statement of main function & got the values for c_Start as 17 & c_stop as 660950030..are these values of any use? can we calculate time or no of clock cycles from these values?

what is the default clock period for tiva c??

Hi Rajat,

If the code does not call any SysCtlClockSet function then PIOSC of 16MHz is the default clock for the TIVA-C devices.

with respect to the timer.

The default timer clock is the system clock. So whatever you set the system clock frequency as is the timer clock as well on TM4C123 devices. E.g for 80MHz system clock the clock time period is 12.5ns, which would be the default clock for timer.

Regards

Amit

Hii Amit,

Thanx for your help & i used 16 MHz as default to calculate time & i am getting the approx correct answer.