ad7674: Read data when the board is used as a stand-alone board

Document created by analog-archivist Employee on Feb 23, 2016
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Problems with the Eval-AD7674 evaluation board.
It is not possible to read data when the board is used as a stand-alone board.
DBUSY (P2.33) and D11 (pin 22 of AD7674) have strange behaviour when the AD7674
is working in mode 0> I can send you an e-mail with more details and pictures
about this problem.


1. 18-bit - The board can be used in stand alone for 18-bit but a new EPROM
needs to be sent to work properly. The TEK0000_C file is showing this issue.
Basically the board is used universally for our 16 and 18-bit boards and when
D1 goes high in 18-bit mode (and it will since this is one of the LSBs and in
the noise) the board thinks you are selecting serial mode and then you see the
burst of SCLKs on the SCLK pin, D11/SCLK, pin 22. I can send you a new EPROM if
18-bit is what you are interested in.

2. For 16-bit interface, you need to control the SER/~PAR on the dip switch,
S16, position 8. The FPGA will just latch the new data when the SER/~PAR state

3. 8-bit or byte wide interface is not so simple since you need to control not
only the SER/!PAR wire which is easy but also pin 9 or D0 on the eval board
schematic (again originally for our 16-bit ADC). Take a look at a 16-bit ADC
such as the AD7677 so you can reference the pins I am talking about. You will
see that pin 8 is SER/!PAR on AD7677 and D1/A0 on AD7674. Also pin 9 is D0 on
AD7677 and D2/A1 on AD7674. The A0/A1 are needed to control the 3 bytes.

4. The AD7621 should work fine. Do you have the control boar to use as a
reference? We can loan one to you if you do not wish to purchase one. Just to
make sure the board is working properly our evaluation SW has histogram in
distribution and time domain also AC testing in time and frequency domains as
well as an over sampling routine using a digital filter.