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SOFTWARE CONTROL (PCM1780/82)

Register Write Operation

MSB

0

IDX6

IDX5

IDX4

IDX3

IDX2

IDX1

IDX0

D7

D6

D5

D4

D3

D2

D1

D0

0

0

LSB

Register Index (or Address)

Register Data

R0001-01

IDX0

D7

D6

D4

D5

D3

D2

D1

D0

0

MS

MC

MD

X

0

IDX6

X

IDX1

IDX2

IDX3

IDX4

IDX5

IDX6

X

T0048-01

Control Interface Timing Requirements

PCM1780, PCM1781, PCM1782

SLES132A – MARCH 2005 – REVISED APRIL 2005

The PCM1780/82 has many programmable functions that can be controlled in the software control mode; the

functions are controlled by programming the internal registers using MS, MC, and MD.

The serial control interface is a 3-wire serial port which operates asynchronously to the audio serial interface.

The serial control interface is used to program the on-chip mode registers. The control interface includes MD

(pin 4), MC (pin 3), and MS (pin 2). 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. MS is the select input, used to enable the mode control

port.

All write operations for the serial control port use 16-bit data words. Figure 24 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 25 shows the functional timing diagram for writing to the serial control port. MS is held at a logic-1 state

until a register needs to be written. To start the register write cycle, MS 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, MS is set to logic 1 to latch the data into the indexed mode control register.

Figure 24. Control Data Word Format for MD

Figure 25. Register Write Operation

Figure 26 shows a detailed timing diagram for the serial control interface. These timing parameters are critical for

proper control port operation.

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