Texas Instruments TI-89

5
TI
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89 / TI
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92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
2. The 68000 TI AMS Operating System Overview
The AMS calculator Operating System (OS) implements a classic cooperative
event-driven architecture. The event manager interfaces with the device drivers
to determine when something important has happened such as a keypress or a
timer interrupt. This information is then packaged into an event message and
sent to the application currently active in the calculator screen. An application
reacts to event messages by performing some action such as moving its cursor
or repainting its window. After responding to an event message, the application
then returns to the event manager and awaits the next event. The event manager
puts the calculator into low power mode until another event occurs. This process
is illustrated in Figure 2.1.
event occurs
Event
Mana
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er
Handle
event
Decode
and
p
acka
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e
event
does not
know how
com
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leted
com
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leted
Default
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A
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Figure 2.1: AMS Event Handler