I am trying to drive a ADG725 with a Microchip PIC (3.3 Volt) and I am having trouble getting the multiplexer to respond. I have hooked up an o-scope to the SYNC, DIN, and SCLK lines and I can see the SYNC line go low, followed by 8 pulses on the clock line while the data line stays at 0. In theory this
should connect S1A – DA, S1B – DB. Is there a frame or start bit that I am missing in my SPI protocol?