3-wire Serial Programming Interface

The WEA1R8SPI55 is a cascade of flip flops, sharing the same clock, in which the output of each flip-flop is connected to the input of the next flip-flop in the chain, resulting in a circuit that shifts by one position the “bit array” stored in it, “shifting in” the data present at its input and ‘shifting out’ the last bit in the array, at each transition of the clock input. The WEA1R8SPI55 contains an 8-bit serial-in, serial-out shift register that feeds an 8-bit, D-type storage register on the rising edge of the clock (SCK).