AD7923_11 datasheet(21/24 Pages) AD

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AD7923

Rev. C | Page 21 of 24

SCLK

DOUT

DIN

t11

tQUIET

tCONVERT

THREE-

STATE

ZERO

ADD1

ADD0

DB11

DB10

DB4

DB3

DB2

DB1

DB0

THREE-

STATE

2 IDENTIFICATION

BITS

ZERO

WRITE

SEQ1

DONTC

ADD1

ADD0

CODING

DONTC

t10

Figure 27. Serial Interface Timing Diagram

116

SCLK

VALID DATA

DOUT

POWER-UP

DIN

tCYCLE 5s MIN

tQUIET MIN

Figure 28. General Timing Diagram

MICROPROCESSOR INTERFACING

The serial interface on the AD7923 allows the part to be directly

connected to a range of many different microprocessors. This

section explains how to interface the AD7923 with some of the

more common microcontroller and DSP serial interface protocols.

AD7923-to-TMS320C541

The serial interface on the TMS320C541 uses a continuous

serial clock and frame synchronization signals to synchronize

the data transfer operations with peripheral devices like the

AD7923. The CS input allows easy interfacing between the

TMS320C541 and the AD7923 without any glue logic required.

The serial port of the TMS320C541 is set up to operate in burst

mode with internal CLKX0 (Tx serial clock on Serial Port 0)

and FSX0 (Tx frame sync from Serial Port 0). The serial port

control register (SPC) must have the following setup: FO = 0,

FSM = 1, MCM = 1, and TXM = 1. The connection diagram is

shown in Figure 29. It should be noted that for signal processing

applications, it is imperative that the frame synchronization

signal from the TMS320C541 provides equidistant sampling.

The VDRIVE pin of the AD7923 takes the same supply voltage as

the TMS320C541. This allows the ADC to operate at a higher

voltage than the serial interface, that is, the TMS320C541, if

necessary.

TMS320C5411

AD79231

CLKX

CLKR

FSX

FSR

VDD

SCLK

DOUT

DIN

1 ADDITIONAL PINS REMOVED FOR CLARITY.

VDRIVE

Figure 29. Interfacing to the TMS320C541

AD792

3-to-ADSP-21xx

The ADSP-21xx family of DSPs is interfaced directly to the

AD7923 without any glue logic required. The VDRIVE pin of the

AD7923 takes the same supply voltage as the ADSP-218x,

which allows the ADC to operate at a higher voltage than the

serial interface, that is, ADSP-218x, if necessary.

The SPORT0 control register should be set up as follows:

TFSW = RFSW = 1, alternate framing

INVRFS = INVTFS = 1, active low frame signal

DTYPE = 00, right justify data

SLEN = 1111, 16-bit data-words

ISCLK = 1, internal serial clock

TFSR = RFSR = 1, frame every word

IRFS = 0

ITFS = 1

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