analog to digital converter adc0804


Posted on Feb 5, 2014

It is 8-Bit, Microprocessor-Compatible, A/D Converters. Data Collection Analog to Digital Conversion and Communicating and It uses an ADC0804 chip to convert from analog to digital, an AT89C2051. The ADC0802 families are CMOS 8-Bit, successive-approximation A/D converters which use a modified potentiometricladder and are designed to operate with the 8080A control bus via three-state outputs.


analog to digital converter adc0804
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These converters appear to the processor as memory locations or I/O ports, and hence no interfacing logic is required. The differential analog voltage input has good common mode-rejection and permits offsetting the analog zero-input voltage value. In addition, the voltage reference input can be adjusted to allow encoding any smaller analog voltage span to the full 8 bits of resolution. The functional diagram of the ADC0802 series of A/D converters operates on the successive approximation principle. Analog switches are closed sequentially by successive-approximation logic until the analog differential input voltage [VlN(+) - VlN(-)] matches a voltage derived from a tapped resistor string across the reference voltage. The most significant bit is tested first and after 8 comparisons (64 clock cycles), an 8-bit binary code (1111 1111 = full scale) is transferred to an output latch. The normal operation proceeds as follows. On the high-to-low transition of the WR input, the internal SAR latches and the shift-register stages are reset, and the INTR output will be set high. As long as the CS input and WR input remain low, the A/D will remain in a reset state. Conversion will start from 1 to8 clock periods after at least one of these inputs makes a low to-high transition. After the requisite number of clock pulses to complete the conversion, the INTR pin will make a high-to-low transition. This can be used to interrupt a...




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