8051 microcontrollers

Pulse Measurement Sensors used for industrial and commercial control applications frequenT1y produce pulses that contain information about the quantity sensed. Varying the sensor output frequency, using a constant duty cycle but variable frequency pulses to indicate changes in the mea­sured variable, is most common. Varying the duration of the pulse width, resulting in constant frequency but variable duty cycle, is also used. In this section, we examine programs that deal with both techniques. Measuring Frequency Timers TO and T 1 can be used to measure external frequencies by configuring one timer as a counter and using the second timer to generate a timing interval over which the first can count. The frequency of the counted pulse train is.then Unknown frequency = Counter/timer For example, if the counter counts 200 pulses over an interval of .1 second generated by the timer. the frequency is UF = 200/. 1 = 2000 Hz Certain fundamental limitations govern the range of fre...

Putting it all Together All of the examples presented to this point have used the free ports (Pl and parts of P3) that the "cheap" design affords. It is clear that to do a real-world design requires the use of additional port chips to enable several functions to be interfaced to the 805 l at one time. Such a design is illustrated in this section, using an 8255 programmable port chip memory mapped at external RAM location 8000h to 8003h. A review of memory map­ping found in Chapter 7 shows that the required address decoding can be done using an inverter to enable external RAM whenever Al5 is low, and the 8255 whenever Al5 is high. Actually, any address that begins with Al5 high can address the 8255; 8000h seems convenient. Ant The example program uses the intelligent LCD display, a coded 16-key keypad, and is capable of serial data communications. This type of design is suitable for many applica­tions where a small, inexpensive, alphanumeric terminal (dubbed the ANT) is ...

Introduction Microcontrollers tend to be underutilized in many applications. There are several reasons for this anomaly. Principally, the devices are so inexpensive that it makes litT1e economic sense to try to select an optimal device for each application. A new microcontroller in­volves the expense of new development software and training for the designers and programmers that could easily cost more than the part savings. Also, some members of the technical community are unfamiliar with the microcontroller due to a dearth of established academic course offerings on the subject. These individuals tend to apply classic eight-bit microprocessor families to problems that are more economically served by a micro­controller. Finally, there is always the pressure to use the latest multibyte processor for marketing reasons or just to keep up with the "state of the art." The result of this application pattern is that Microcontrollers tend to become obsolete at a slower rate than ...