Flags are similar to binary semaphores. There are two differences:

1. you can wait, check, set or reset several flags at one time;
2. after accepting flags their values do not change.

Flags can be useful when a task requires the results of several tasks. For example: to calculate some physical parameters a task needs information about the temperature, pressure and humidity. Each of these parameters is measured in its own task which sets a flag when measurement is complete.

#include <osa.h>
 
OST_FLAG8   F_Sensors;
 
#define  TEMPERATURE_MEASURED   0x01
#define  PRESSURE_MEASURED      0x02
#define  HUMIDITY_MEASURED      0x04
 
void Task_Calc (void)
{
    for (;;) {
        // Wait for all measurements complete
        OS_Flag_Wait_AllOn(F_Sensors, TEMPERATURE_MEASURED | PRESSURE_MEASURED | HUMIDITY_MEASURED);
        OS_Flag_Clear(F_Sensors, TEMPERATURE_MEASURED | PRESSURE_MEASURED | HUMIDITY_MEASURED);
 
        // Now we can calculate
        ...
    }
}

There are three types of flags: 8-, 16- and 32-bit.

OST_FLAG      MyFlag1;	//  8-bit flags
OST_FLAG16    MyFlag2;	// 16-bit flags
OST_FLAG32    MyFlag3;	// 32-bit flags

It is possible to use different size of flags at the same time.

Flags can be allocated in any memory bank, e.g.:

bank2    OST_FLAG16   MyFlag;