AD7705BN datasheet(33/44 Pages) AD

33 / 44 page

AD7705/AD7706

Rev. C | Page 33 of 44

CONFIGURING THE AD7705/AD7706

The AD7705/AD7706 contain six on-chip registers that the user

can access via the serial interface. Communication with any of

these registers is initiated by first writing to the communication

configure registers after a power-up or reset on the AD7705;

similar procedures apply to the AD7706.

The flowchart also shows two read options—one polls the DRDY

pin, and the other interrogates the DRDY pin. In addition,

Figure 21 shows a series of words that should be written to the

registers for the following operating conditions: Gain 1, no

filter sync, bipolar mode, buffer off, clock of 4.9512 MHz, and

output rate of 50 Hz.

POWER-ON/RESET FOR AD7705

CONFIGURE & INITIALIZE

μC/μP SERIAL PORT

WRITE TO COMMUNICATIONS REGISTER SELECTING

CHANNEL & SETTING UP NEXT OPERATION TO BE A

WRITE TO THE CLOCK REGISTER (20 HEX)

WRITE TO CLOCK REGISTER SETTING THE CLOCK

BITS IN ACCORDANCE WITH THE APPLIED MASTER

CLOCK SIGNAL AND SELECT UPDATE RATE FOR

SELECTED CHANNEL (0C HEX)

WRITE TO COMMUNICATIONS REGISTER SELECTING

CHANNEL & SETTING UP NEXT OPERATION TO BE A

WRITE TO THE SETUP REGISTER (10 HEX)

WRITE TO SETUP REGISTER CLEARING F SYNC,

SETTING UP GAIN, OPERATING CONDITIONS &

INITIATING A SELF-CALIBRATION ON SELECTED

CHANNEL (40 HEX)

POLL DRDY PIN

YES

WRITE TO COMMUNICATIONS REGISTER SETTING UP

NEXT OPERATION TO BE A READ FROM THE DATA

READ FROM DATA REGISTER

WRITE TO COMMUNICATIONS REGISTER SETTING UP NEXT

OPERATION TO BE A READ FROM THE COMMUNICATIONS

READ FROM COMMUNICATIONS REGISTER

POLL DRDY BIT OF COMMUNICATIONS REGISTER

WRITE TO COMMUNICATIONS REGISTER SETTING UP

NEXT OPERATION TO BE A READ FROM THE DATA

START

READ FROM DATA REGISTER

DRDY

LOW?

YES

DRDY

LOW?

Figure 21. Flowchart for Setting Up and Reading from the AD7705

AD7705BN Datasheet(PDF) 33 Page - Analog Devices

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