Datasheet

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SERIAL CONTROL INTERFACE
REGISTER WRITE OPERATION
IDX5IDX60 IDX4 IDX2IDX3 IDX1 IDX0 D7 D6 D5 D4 D3 D2 D1 D0
MSB
Register Index (or Address) Register Data
LSB
0 D7 D6 D5 D4 D3 D2 0 IDX6D1 D0X X XIDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0
ML
MC
MD
PCM1742
SBAS176A – DECEMBER 2000 – REVISED APRIL 2005
The serial control interface is a 3-wire serial port that operates asynchronously to the serial audio interface. The
serial control interface is used to program the on-chip mode registers. The serial control interface includes
MD (pin 13), MC (pin 14), and ML (pin 15). MD is the serial data input, used to program the mode registers; MC
is the serial bit clock, used to shift data into the control port; and ML is the control-port latch clock.
All write operations for the serial control port use 16-bit data words. Figure 23 shows the control data word
format. The most significant bit must be a 0. Seven bits, labeled IDX[6:0], 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 23. Control Data Word Format for MD
Figure 24 shows 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.
Figure 24. Register Write Operation
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