11 - More devices

Abstract

This chapter discusses some complex devices that may be included in an embedded system. Many embedded systems use counter devices, timer devices, and calendar devices; these are introduced in the chapter. The counter device is incorporated into a model of a conveyor belt in a factory where the counter counts the number of objects that pass along the conveyor. The chapter illustrates a model of a kiln is as an example of hardware that is controlled by an embedded computer control system. The specifications of these devices are also given. Finally, the chapter demonstrates how a timer may be used to make it appear that a computer is performing a number of programs simultaneously, a technique called multitasking. However, if the time between successive objects is short and the computer has many tasks to do, it may not be able to keep up with the flow of objects. Alternatively, the job of counting can be delegated to a separate piece of hardware, a counter device. The most common use of this device is to generate an interrupt request to the G80 when a certain number of objects have been counted. The interrupt service routine does whatever is required when the required count has been reached.