Interfacing Microcomputers with Laboratory Signals
We have seen that the measurement or control functions of laboratory instrument circuits produce or utilise signals which may be voltages, currents or pulses, while the microcomputer is a byte oriented device which produces or uses 8-bit parallel binary signals. To enable the signals of an instrument to form input or output data for a computer a third device is needed to translate one type of signal into the other. Such a device is called an interface and its role is illustrated in fig 7.1. An instrumental signal may be a constant value or may be time dependent, while the computer’s signal must be one or more bytes specified at a particular instant of time. For this reason the translation carried out by the interface must be triggered in some way, either by the computer or by the laboratory instrument. In describing the basic types of laboratory interfaces (section 7.1), we shall assume that the computer initiates the translation process with a logic signal on a single control line (using, for example, the software control described in section 6.3). The subject will be considered in more detail in section 7.4.
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