Ian,

Generally, whenever a RTOS is mentioned, it tends to imply a pre-emptive task switcher - Real Time suggests that tasks will be activated in a timely and consistant manner. A co-operative tasker I would not call a RTOS.

I doubt if I would call my priority system 'fancy'! By fancy, I mean round robin,priority inversion etc.

He's how I do it in 'c' and it's also quite easy to code in assembler and compact!


[pre]
while(1)
{


if (tick_flag != 0)
{
tick_flag=0;
kick_dog();
task_dispatch(); // well....
}
}
}


//
// reload the watchdog timer so he doesn't reset us....
//
void kick_dog(void)
{
EA = 0;
//put watchdog reload code in here
EA = 1;
}


void task_dispatch(void)
{
// scan the task bits for an active task and execute it


char xtask;



/* take care of the task timers. if the value ==0 skip it
else decrement it. If it decrements to zero, activate the task associated with it */
xtask = 0;


while (xtask < NUM_TASKS )
{
if (task_timers[xtask] !=0 )
{
task_timers[xtask]--; /* dec the timer */
if (task_timers[xtask] == 0 ) set_task(xtask); /* if ==0 activate the task bit */
}

xtask++;
}


xtask=0; /* start at the most significant task */
while (xtask < NUM_TASKS )
{
if ((task_bits & bit_mask[xtask]) != 0 ) break; /* if activate task found..*/
xtask++; /* else try the next one */
}
switch(xtask) /* if task bit is active..execute the task */
{
case 0:
task0();
break;
case 1:
task1();
break;
case 2:
task2();
break;
case 3:
task3();
break;
case 4:
task4();
break;
case 5:
task5();
break;
case 6:
task6();
break;
case 7:
task7();
break;
default:
break; /* no task was active!! */
}
}
/*****************************************************************************************


Sets the run flag for the supplied task number.
be sure not to pass a task# > 7 as the number is masked and will wrap around!


******************************************************************************************/
void set_task(char tsk)
{
EA=0; /* no interrupts */
task_bits |= bit_mask[tsk]; /* sets a task bit */
EA=1;
}
/*****************************************************************************************


Resets the run flag for the supplied task number.


******************************************************************************************/
void reset_task(char tsk)
{
EA=0;
task_bits &= (~bit_mask[tsk]); /* resets a task bit */
EA=1;
}
void T0_int(void) interrupt 1
{
static data char ticker = 0;

TR0=0;
TL0 = (1 - TIME_TICK);
TH0 = (1 - TIME_TICK)>>8;
TR0=1; /* set the timer running */
if (ticker !=0)
{
ticker--;
}
else
{
tick_flag=1; /* set the tick flag */
ticker = 10;
}
}

[/pre]