Instrument Control (GPIB, Serial, VISA, IVI)

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Why would the TNT4882 be responding inconsistently.

I am using a microcontroller to talk to the TNT4882. During write cycles, the microcontroller correctly sends the address, csn, wrn and data signals to the TNT and all the signals are within tolerances of the generic mode ac timing characteristics from the tnt data sheet. However, the TNT does not consistently respond with the RDY1 signal which would indicate the data had been latched. The RDY1 only seems to work correctly when I am talking to specific registers, for example, I have always been able to load data into FIFOA, FIFOB, INTR, HSSEL, ADR, and the TIMER registers, but when I address any other register, the TNT fails to respond. On a read cycle, the TNT has the tendency to work even less, th
e only registers I have been able to read from are the FIFOA and FIFOB registers. Once again, the microcontroller correctly asserts the address, csn, rdn, and data signals while the TNT fails to respond with a RDY1 pulse. What could be causing this inconsistency?
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As a first source of trouble shooting and reference, I would suggest looking through the following resources.
TNT4882 Manual --> http://www.ni.com/pdf/manuals/320724.pdf
General Register Level Programming Information --> http://ni.com/support/gpib/reg_prog.htm
Basic shell program for interfacing to a TNT4882 cihp --> ftp://ftp.ni.com/support/gpib/misc/ESP-488.ZIP

The specific pages of interest for you will be 5-3, 5-4, and B-4, which all deal with the RDY1 line. If, after reading through the manual and other resources, you still have questions, please let me know.

Ryan Tamblin
Applications Engineer
National Instruments
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