User`s guide

Overview of Thread Scheduling
Thread Scheduling 4-5
ensures that the PRD_swi software interrupt can preempt those routines
when the next system tick occurs and PRD_swi is posted again.
4.1.3 A Comparison of Thread Characteristics
Table 4-1 provides a comparison of the thread types supported by DSP/BIOS.
Table 4-1. Comparison of Thread Characteristics
Notes: 1) If you disable the TSK Manager in the Property dialog for the TSK Manager, IDL threads use the system stack.
2) See section 4.3.7, Saving Registers During Software Interrupt Preemption, page 4-37, for a list of saved registers.
Characteristic
HWI SWI TSK IDL
Priority Highest 2nd highest 2nd lowest Lowest
Number of priority
levels
DSP-dependent 15. Periodic func-
tions run at priority of
the PRD_swi SWI
object. Task sched-
uler runs at lowest
priority.
16 (Including 1
for the ID loop)
1
Can yield and pend No, runs to
completion except
for preemption
No, runs to
completion except
for preemption
Yes Should not; would
prevent PC from
getting target
information
Execution states Inactive, ready,
running
Inactive, ready,
running
Ready, running,
blocked,
terminated
Ready, running
Scheduler
disabled by
HWI_disable SWI_disable TSK_disable Program exit
Posted or made
ready to run by
Interrupt occurs SWI_post,
SWI_andn,
SWI_dec, SWI_inc,
SWI_or
TSK_create main() exits and no
other thread is cur-
rently running
Stack used System stack
(1 per program)
System stack
(1 per program)
Task stack
(1 per task)
Task stack used by
default (see Note 1)
Context saved
when preempts
other thread
Customizable Certain registers
saved to system
stack (see Note 2)
Entire context
saved to task
stack
--Not applicable--