In the data acquisition system, the speed and accuracy of the A / D conversion determines the speed and accuracy of the acquisition system. MAX197 is a high-speed A / D conversion chip with 12-bit measurement accuracy introduced by Maxim. It requires only a single power supply and the conversion time is very short (6ms). It has 8 input channels and also provides a standard parallel interface-8 The three-state data I / O port can be directly interfaced with most single-chip microcomputers, which is very convenient to use.
Introduction to MAX197
The basic principle of MAX197 conversion
MAX197 can complete the A / D conversion function independently without external components. It can be divided into internal sampling mode and external sampling mode, the sampling mode is determined by the D5 bit of the control register. In the internal sampling control mode (control position 0), the sampling interval is started by the write pulse, and after an instantaneous sampling interval (3ms when the chip clock is 2MHz), the A / D conversion starts. In the external sampling mode (D5 = 1), two write pulses control the sampling and A / D conversion respectively. When the first write pulse occurs, write ACQMOD to 1 to start the sampling interval. When the second write pulse occurs, write the control word ACQMOD to 0, MAX197 stops sampling and starts A / D conversion. The time interval between these two write pulses is one sampling time. When a conversion is completed, the corresponding INT pin of MAX197 is set low to inform the processor that the conversion result can be read. The timing of data conversion in the internal sampling mode is very strict for the conversion from analog to digital. Since the digital signal output pins of the MAX197 are multiplexed, the timing requirements are particularly important to read the conversion results correctly. Before a sampling starts, these control words can be written into MAX197 through the 8-bit data line of the microcontroller to initialize the corresponding parameters. Then according to a certain timing sampling and conversion.
Pin diagram of MAX197
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