Hi Ian, The ADS8920B can be used with as little as 3-wires. Figure 88 in the datasheet shows the minimum-pin interface. The CONVST pin is tied to /CS, /RST is pulled high, and if you do not have a 4th wire and can use the default configuration of the ADC on power-up, you can tie the SDI pin to ground. Refer to Figure 56 for the protocol (note this shows 22 SCLK's, but you only need 16 SCLK's to read the conversion result). The CONVST pin starts the internal conversion process. Controlling this separately from the /CS pin provides timing flexibility. You should be able to share the same SCLK with other devices as long as you have separate /CS controls. You will need to make sure that none of the timing requirements are violated. There is a 'quiet' period when no digital signals should toggle around the rising edge of CONVST (/CS); refer to Figure 46 in the datasheet. Thanks, Keith N. Precision ADC Applications
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