Texas Instruments TMS320 User Manual

Overview of Thread Scheduling
Thread Scheduling 4-5
❏ PRD. Use PRD functions when you want a function to run at a rate based
on a multiple of the on-device timer’s low-resolution rate or another event
(such as an external interrupt). These functions run as SWI functions.
❏ PRD versus SWI. All PRD functions run at the same SWI priority, so one
PRD function cannot preempt another. However, PRD functions can post
lower-priority software interrupts for lengthy processing routines. This
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, IDL threads use the system stack.
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)

Texas Instruments TMS320 Specifications

General

Brand	Texas Instruments
Model	TMS320
Category	Computer Hardware
Language	English