All write operations for the serial control port use 16-bit data words. Figure 26 lists the control data word format. The most significant bit must be a 0. There are seven bits, labeled IDX[6:0], that set the register index (or address) for the write operation. The least significant eight bits, D[7:0], contain the data to be written to the register specified by IDX[6:0].
Figure 27 lists the functional timing diagram for writing to the serial control port. ML is held at a logic 1 state until a register needs to be written. To start the register write cycle, ML is set to logic 0. Sixteen clocks are then provided on MC, corresponding to the 16 bits of the control data word on MD. After the sixteenth clock cycle has completed, ML is set to logic 1 to latch the data into the indexed mode control register.