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MODE CONTROL

SPI CONTROL INTERFACE

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

PCM1680

SLES133 – MARCH 2005

The PCM1680 has many programmable functions which can be controlled in the software control mode. The

functions are controlled by programming and reading the internal registers using the SPI or I

two interfaces for mode control can be selected by MSEL (pin 14). The functions of pins 2, 3, and 4 are changed

by MSEL selection as shown in Table 4.

Table 4. Interface Mode Control

PIN FUNCTION

MSEL

INTERFACE MODE

PIN 2

PIN 3

PIN 4

LOW

SPI

MS

MC

MD

HIGH

ADR

SCL

SCA

The SPI control interface of the PCM1680 is a 3-wire synchronous serial port that operates asynchronously to

the serial audio interface. The SPI 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 control port for the serial bit clock, used to shift in the serial data, and MS is the control port

for mode control select, which is used to enable the mode control.

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 is a fixed 0 for the write operation. 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 clock cycles are

then provided on MC, corresponding to the 16 bits of the control data word on MD. After the completion of the

sixteenth clock cycle, 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. Write Operation Timing

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