Hi Khoi, I would use a single GPIO pin from the MCU to connect to all three SYNC pins, keeping the trace length(s) to each ADC about the same. This way you guarantee that all three ADS1257 's receive the SYNC pulse at the same time. If you configure each ADC to operate at the same data rate, you use the same clock for all three ADCs, and you synchronize them at the same time, then the /DRDY interrupts from all three ADCs will occur at the same time and you don't have to monitor each /DRDY signal independently. However, if you have spare GPIO pins there is no harm in connecting all three /DRDY outputs to the MCU to give you the ability to operate each ADC at a different data rate. From a programming perspective, the interface is the same and the only difference is in the register map settings. For example, there are fewer MUX register and IO register options but otherwise the same software could be used for both. Unfortunately, we haven't provided much example code for either of the ADS1256 or ADS1257 devices, but you could reference this E2E thread for one additional example: e2e.ti.com/.../1182307
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