AD7730: RDY signal not working

Q 

I try to program the AD7730 according to the example on page 36-37 of the data
sheet. The AD7730 is connected to a atmel at90s8535 microprocessor which
programs the registers. If I connect the RDY pin of the AD7730 to a
oscilloscope I dont see the signal going low (as in Wait for RDY low), it
always stays high. Is it neccesary to add a pull up or pul down resistor of to
use a buffer of something like that?

 

A 

Pull up/down resistors are not required at the RDY line.

A few notes:
f you have established proper communication between the AD7730 and your micro,
you should be able to read back the contents of the registers that you have
programmed?? Is that possible.

If you cannot, then you will need to verify your code by connecting a scope to
SCLK, DIN of the ADC to verify that the correct information is being sent to
the ADC.

If you succeed in reading back the contents of the ADC registers, then you
should scope the RDY line after initiating a conversion…try changing to
continuous conversion mode, and you should see RDY changing at the o/p data
rate.

1) The following conditions could prevent the /RDY line from updating.
* The /RESET is pulled low
* The FSYNC is pulled set
* The STBY bit is set or the STANDBY pin is low
* The /RDY pin is pulled  low externally

2) In the error condition, try communicating with the part, for example write
to the communications register and try to read back from the Communications and
the setup register. Does the part respond correctly?.

3) Look for the possibility that you inadvertently write to the Communications
register. We generally recommend that DIN is pulled high when the part is idle
to ensure that any activity on SLCK is ignored.

4) Try resetting the digital interface by writing 32 1s to the part. Does this
recover correct operation?