Saving Power - Husky MP2500 Manual

32.3 Saving power

IMPORTANT
To make the best use of its battery capacity, MP2500 conserves power in a
variety of ways, some obvious, some not so obvious. Most of these
mechanisms are entirely automatic and have very little impact on users.
However, if you are writing programs, you may need to know about the
mechanisms described here.
The power save modes and power down (off) timeout require the unit to
become 'idle'. This means that although the processor can be, for example,
"waiting for a key", it must not do any significant input / output. The use of
any of the following services will override automatic power saving functions:
• Screen services via INT 0H or direct writing to video RAM
• Disk services via INT 13H
• Serial communications via INT 14H or direct access to UARTs
• BIOS extension services via INT 15H
• Time and Date services via INT 1AH
• DOS services via INT 21H
• Access to 8253 sound
If your code is written for a compiler which uses 'standard library routines'
you may not even be aware that these services are being used. Generally
any ongoing I/O (keyboard, screen and disk) functions will prevent the BIOS
from assuming the idle state.
The BIOS can be instructed to allow power save even if some of these
functions are in use by using INT 15H function AH=8CH (Get/Set power
save entry flag) this is an advanced feature and should only be used with
great care.
Please refer to Appendix G for more details on comparison with H
USKY
FS handheld computers.
The power-saving aspects fall into the following categories:
306 H MP2500 System Developer's Guide
USKY