Hardware for data acquisition and control

There are two styles of hardware for using a microcomputer to acquire data and control equipment. One is exemplified by the IBM-PC system you have used in the laboratory. The ADC, the DAC and the digital I/O cards are inside the computer and are under direct control of the microprocessor. They have control and data registers which are directly addressable via the buss. External devices (sensors, switches, etc) are connected to the cards. Creative programming can turn the computer into, for example, an oscilloscope (ADC and display) or a signal generator (DAC) as the laboratory exercises have shown.

Other buss systems are in use which, like the slots in the IBM-PC, allow a microprocessor to be connected to various data acquisition and control devices by simple board replacements. Some of the more widely used ones are S100, STDBUS, MULTIBUS, and QBUS.

The second style is to have a separate box next to the computer which has the ADCs, DACs, digital I/O lines and a programmed microprocessor controller. It communicates with the computer via a serial or parallel communication system (Section 9.2 has a description of a parallel system). The box takes care of the data acquisition and control while the computer is used to send control bytes to tell the box what to do and to receive the data for further processing. The limitation of this style is in the speed of communication to the computer and in the number of things the box has been preprogrammed to know how to do.