ABSTRACT
ThreadX sets the internal system clock to zero during application initialization, and each timer-tick increases the clock by one. The internal system clock is intended for the sole use of the developer. Applications can perform exactly two actions on the internal system clock: either read the current clock value, or set its value. Fast response to asynchronous external events is the most important function of real-time, embedded applications. However, many of these applications must also perform certain activities at predetermined intervals of time. Time intervals are measured by periodic timer interrupts. Each timer interrupt is called a timer-tick. Timer expiration intervals are specified in terms of timer-ticks. The timer count starts at the specified expiration value and decreases by one on each timer-tick. Application timers execute in the order in which they become active. The characteristics of each application timer are found in its Application Timer Control Block.
