why mdloutput is not executing according to step size mentioned in configuration parameters window?

Hi everyone, i have some data in json file and i'm passing the json file name through s-function mask, also i have one dll file which is needed for some functionality.

For s-function setting input and output im using mdlInitializeSizes() and to load dll and getProcAddress im using mdlstart() function both are working fine,but in mdloutput im using one condition like

int count =(int)((sim_time-base_time)/(sync_time));

for(i = 0; i < count; i++);

{

//im calling some functions mentioned in dll file

base_time=sim_time;

}

where sync_time is 1us which i will get it from dll and base time is initially 0 and sim_time=ssGetT(S);

in configuration parameter window i'm using fixed step for that start time and stop time are 0.0 and 1.0 respectively and step size of 0.5us along with this i'm selecting ode1(Euler) as my solver.when i run my module im getting sim_time=0 in mdloutput function which is correct after that its directly executing mdlTerminate function. why mdloutput is executing only once please help it out i will attch part of my mdloutput code along with this.