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>Unclearence regarding some Pins of AD7634


in my project I am using the AD7634 as AD-Converter. The AD7634 is configured in 18bit Warp Mode, parallel interface, +10/-10V input signal.

I want to control the AD7634 with the µC AT32UC3A Atmel Device.

There are four pins from the AD7634 where I don't have the clearence what to do with them, or how should I connect them to the µC.

The Pins are: Busy (No. 29), CNVST (No. 35), RD (No. 31) and CS (No. 32).

The idea was to control the AD7634 through the Pins Busy and CNVST. So if the Busy Pin is Low, the parallel datainterface is enabled (data-ready clock signal). Through CNVST Pin my µC can start the conversion.

First question is, can I connect the Busy and CNVST Pins to any IO-Pins of my µC, or do they need special pins?

The second question is, How do I use the RD and CS Pins? Have I to use them, or can I just leave them open? In the datasheet I read, that both pins should be open, so the parallel interface can be enabled, but I enabled the parallel interface though the Pins 3 and 4. What am I misreading and misunderstanding. Please explain.

many thanks and best regards, mikhail.

  • Hi Mikhail,

    We are looking into this. We'll get back to you soon.



  • Hi,

    The BUSY pin on the ad7634, remains high when a conversion has started and until it is complete, data is latched on the on chip shift register. Falling edge of BUSY indicates the data is ready.

    A falling edge of CNVST initiates conversion, puts the sample and hold into its hold state. Please make sure to follow the timing specifications and abs max/min voltages when connecting it to ucontroller.

    The CS chip select and RD read data, are indicators that data can be latch out. CS and RD controls interface. CS and RD can be tied together.

    Yes you're right that the interface mode was selected already on pins 3 and 4, this is either parallel or serial interface. The digital interface are in high impedance when at least 1, CS or RD, is HIGH.

    The digital pins can interface when they are not in high impedance state.So a high-to-low transition for CS and RD removes the digital interface from high impedance state, now the ad7634 can communicate with ucontroller.



  • Thank you for answering.

    So I can tie RD and CS together and set them both to High, when I want to control the AD7634 with my µC? Or I can tie them together, connect to an IO Pin of my µC and set them to High with the Controller, and then I can start using the AD7634?

    best regards.

  • Hi,

    Just to clarify, to enable the parallel output bus, CS and RD should be Low.

    You can choose to tie RD and CS low which enables the parallel output bus, to continously read data.

    I think it would be better to tie them together and connect to an I/O of the microcontroller so you can have better control the status of these pins.



  • Thank you very much, that was the same thing I wanted to do, but I was unsure.

    Just to clarify, I can do the same with the MODE,  Warp and Impulse pins, so I can switch between different modes of operation?

    Best regards.

  • Hi,

    You  can choose to do that. You may also take a look on the Evaluation board for the PULSAR 48 lead ADC document, which includes the AD7634 to give you idea on how the connections were made. Please refer to link below.