8051 microcontrollers

Serial Data Transmission The hallmark of contemporary industrial computing is the linking together of multiple processors to form a "local area network" or LAN. The degree of complexity of the LAN may be as simple as a microcontroller interchanging data with an I/O device, as compli­cated as linking multiple processors in an automated robotic manufacturing cell, or as truly complex as the linking of many computers in a very high speed, distributed system with shared disk and 110 resources. All of these levels of increasing sophistication have one feature in common: the need to send and receive data from one location to another. The most cost-effective way to meet this need is to send the data as a serial stream of bits in order to reduce the cost (and bulk) of multiple conductor cable. Optical fiber bundles, which are physically small, can be used for parallel data transmission. However, the cost incurred for the fibers, the termina­tions, and the optical interface to the...

Timing Subroutines Subroutines are used by call programs in what is known as a "transparent" manner-that is, the calling program can use the subroutines without being bothered by the details of what is actually going on in the subroutine. Usually, the call program preloads certain locations with data, calls the subroutine, then gets the results back in the preload locations. The subroutine must take great care to save the values of all memory locations in the system that the subroutine uses to perform internal functions and restore these values be­fore returning to the call program. Failure to save values results in occasional bugs in the main program. The main program assumes that everything is the same both before and after a subroutine is CALLED. Finally, g00d documentation is essential so that the user of the subroutine knows pre­cisely how to use it. Time Delays Perhaps the most-used subroutine is one that generates a programmable time delay. Time delays may be...

Introduction In this chapter a hardware configuration for an 805 I microcontroller, which will be used for all of the example applications in Chapters 8 and 9, is defined. Programs that check the initial prototype of the design (debugging programs) are given in this chapter, followed by several common subroutines that can be used by programs in succeeding chapters. The design of the microcontroller begins with an identified need and a blank piece of paper or computer screen. The evolution of the microcontroller follows these steps: 1. Define a specification. 2. Design a microcontroller system to this specification. 3. Write programs that will assist in checking the design. 4. Write several common subroutines and test them. L00 The most important step is the first one. If the application is for high-volume produc­tion (greater than 10000 units). then the task must be very carefully analyzed. A precise or "tight" specification is evolved for what will become a m...