I'm probably going to do a bad job of explaining this as it has a bunch of components to it, but I've figured out the operating system (by the way the name of the OS is OSKAR) task scheduling system. When I have a high enough level of enthusiasm I'll document this properly in the wiki, but for now here's the quick run-down.
Each processor in the DME receives an external timer interrupt from the programmable interrupt timer 1024 times per second (e.g. approximately every millisecond).
The interrupt is handled here:
So this function fires every 1ms, and in it it does some important high frequency things like update the system timertics variables, sync the values in the dual-ported RAM to local copies of the variables, etc.
Every 2ms it calls sys_process_scheduled_tasks() which checks all scheduled tasks, updates the delay timers on each task and reschedules periodic tasks.
Every time the function runs, and provided there are no other active interrupts, the tasks are actually dispatched via sys_dispatch_tasks which in turn calls sys_task_dispatcher.
Both of these functions are below:
There is also a function to schedule a task in the first place:
And to cancel tasks:
The details of the tasks are stored in a pointer array in the program ROM (0x0003d810 in Master) which in turn points to a table of structs
The array of structs starts at 0x0003d798 (in Master program ROM)
And this is what I've figured out of the structure so far:
It's important to note that sys_process_scheduled_tasks runs every 2ms (every other time the timer interrupt fires) so the period and the initial delay of each task is specified in units of 2ms. e.g. task_10ms has period_2s set to 0x0005:
The task manager can manage up to 32 different tasks and can schedule up to 8 of them at once for execution.
Each processor in the DME receives an external timer interrupt from the programmable interrupt timer 1024 times per second (e.g. approximately every millisecond).
The interrupt is handled here:
So this function fires every 1ms, and in it it does some important high frequency things like update the system timertics variables, sync the values in the dual-ported RAM to local copies of the variables, etc.
Every 2ms it calls sys_process_scheduled_tasks() which checks all scheduled tasks, updates the delay timers on each task and reschedules periodic tasks.
Every time the function runs, and provided there are no other active interrupts, the tasks are actually dispatched via sys_dispatch_tasks which in turn calls sys_task_dispatcher.
Both of these functions are below:
There is also a function to schedule a task in the first place:
And to cancel tasks:
The details of the tasks are stored in a pointer array in the program ROM (0x0003d810 in Master) which in turn points to a table of structs
The array of structs starts at 0x0003d798 (in Master program ROM)
And this is what I've figured out of the structure so far:
It's important to note that sys_process_scheduled_tasks runs every 2ms (every other time the timer interrupt fires) so the period and the initial delay of each task is specified in units of 2ms. e.g. task_10ms has period_2s set to 0x0005:
The task manager can manage up to 32 different tasks and can schedule up to 8 of them at once for execution.
. Maybe throw a screenshot of that function up for code review completeness?
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