Software Interrupts
4-28
2) To change the priority of a SWI object, drag the software interrupt to the
folder of the corresponding priority. For example, to change the priority of
SWI0 to 3, select it with the mouse and drag it to the folder labeled
Priority 3.
Software interrupts can have up to 15 priority levels. The highest level is
SWI_MAXPRI (14). The lowest is SWI_MINPRI (0). The priority level of 0 is
reserved for the KNL_swi object, which runs the task scheduler. See Section
4.3.3, Software Interrupt Priorities and Application Stack Size, page 4-28, for
stack size restrictions. You cannot sort software interrupts within a single
priority level.
The Property window for an SWI object shows its numeric priority level (from
0 to 14; 14 is the highest level). You can also set the priority by selecting the
priority level from the menu in the Property window as shown in Figure 4-6.
Figure 4-6. SWI Properties Dialog Box
4.3.3 Software Interrupt Priorities and Application Stack Size
All threads in DSP/BIOS, excluding tasks, are executed using the same
system stack.
The system stack stores the register context when a software interrupt
preempts another thread. To allow the maximum number of preemptions that
can occur at run time, the required stack size grows each time you add a
software interrupt priority level. Thus, giving software interrupts the same
priority level is more efficient in terms of stack size than giving each software
interrupt a separate priority.
The default system stack size for the MEM module is 256 words. You can
change the sizes in the configuration. The estimated sizes required are
shown in the status bar at the top of the Configuration Tool.
To Next Page
Loading...
Need help?
General
