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

PCM1681

PCM1681-Q1

All write operations for the serial control port use 16-bit data words. Figure 25 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 26 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. 16 clock cycles are then

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

cycle, MS is set to logic-1 to latch the data into the indexed mode control register.

Figure 25. Control Data Word Format for MD

Figure 26. Write Operation Timing

Copyright © 2008, Texas Instruments Incorporated

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