Texas Instruments TI89 Developer Guide - Page 47

5 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 Manager event occurs Idle Decode and package event completed Default event handling Application completed Handle event does not know how Figure 2.1: AMS Event Handler TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001