T-Kernel Specification (1.B0.02)

200 CHAPTER 4. T-KERNEL/OS FUNCTIONS
TPW DOSUSPEND
TPW DISLOWPOW
TPW ENALOWPOW
Suspended state
Switching to low-power mode disabled
Switching to low-power mode enabled (default)
#define TPW_DOSUSPEND 1 Suspended state
#define TPW_DISLOWPOW 2 Switching to low-power mode disabled
#define TPW_ENALOWPOW 3 Switching to low-power mode enabled (default)
• TPW DOSUSPEND
Execution of all tasks and handlers is stopped, peripheral circuits (timers, interrupt controllers,
etc.) are stopped, and the power is cut (suspended). (off pow is called.)
When power is turned back on, peripheral circuits are restarted, execution of all tasks and handlers
is resumed, operations resume from the point before power was cut, and the system call returns.
If for some reason the resume processing fails, normal startup processing (for reset) is performed
and the system boots fresh.
• TPW DISLOWPOW
Switching to low-power mode in the dispatcher is disabled. (low pow is not called.)
• TPW ENALOWPOW
Switching to low-power mode in the dispatcher is enabled. (low pow is called). The default at
system startup is low-power mode enabled (TPW ENALOWPOW).
Each time TPW DISLOWPOW is designated, the request count is taken. Low-power mode is enabled only
when TPW ENALOWPOW is requested for as many times as TPW DISLOWPOW was requested. The maximum
request count is implementation-dependent, but a count of at least 255 times must be possible.
[Additional Notes]
off pow and low pow are T-Kernel/SM functions. See 5.6 for details.
T-Kernel does not detect power supply problems or other factors for suspending the system. Actual
suspension requires suspend processing in each of the peripheral devices (device drivers). The system is
suspended not by calling tk set pow directly but by use of the T-Kernel/SM suspend function.
Copyright c○ 2002, 2003 by T-Engine Forum
T-Kernel 1.B0.02