Digital Electronics: Principles, Devices and Applications

600 Digital ElectronicsV CC3V CC2Micro controller45678CONRSRWEN LCD DisplayD0D1 D2 D3 D4 D5 D6 D79 10 11 12 13 141GNDFigure 14.34LCD display interface with a microcontroller.14.6.6 Interfacing A/D ConvertersA/D converters are used to interface the microcontroller with the analogue world. Figure 14.35 showsthe interface of A/D converter type number AD571 with the microcontroller. AD571 is an eightbitA/D converter. As can be seen from the figure, the data output lines and the control lines of theA/D converter are connected to the microcontroller I/O pins. The microcontroller sends commandssuch as the start of conversion, selection of the input channel if the A/D converter has more thanone input channel, etc. It also senses signals from the A/D converter such as the end of conversionto store the digital bits. In the present case, the microcontroller sends a LOW on the BLANK/DRline to start the conversion process. It then waits for the data ready DR signal to go to LOW.After that, the digital output bits are received by the microcontroller and processed according to thesoftware routine.14.6.7 Interfacing D/A ConvertersWhen interfacing a D/A converter to the microcontroller, the digital data lines and the control lines,such as the start of conversion and chip select lines, are connected to the microcontroller I/O pins.The software routine generates the required signals to start the conversion process. Figure 14.36shows the interface of D/A converter type number DAC 809 with the microcontroller. DAC-809 isa eight-bit D/A converter. Here, the output is current, so a current-to-voltage converter is requiredat the output.