GPIB bus timing

[WH-Tan]

Hello,

I'm new to GPIB register level programming. I have some experience in GPIB but my prior experience was using more higher level programming.  I try to control the GPIB bus with my testing board, which consists of a uC + NAT9914, together with the required transceivers.  The NAT is operating in 9914 mode.

The screen shot I took from a testing result, where I intended to send MTA0, MLA7, DCL, LLO commands over the GPIB bus. Base on those screen shot, can you kindly let me know if the timings are correct, especially DAV, NRFD and NDAC, relative to each other?

The diagram on top is showing 4 bytes sent over GPIB bus (40h, 27h, 14h, 11h) . The diagram at bottom is a zoom-in of first byte (40h). The vertical grid lines interval is 5 us for the top diagram, whereas 500 ns for the bottom one.

 

Thanks very much and best regards,

[Steven_T · Accepted solution]

Hello WH Tan,

I've checked your capture shots and checked the commands that you are sending across the bus.  The controller (is the NAT9914 the controller?) is successfully sending all of the GPIB addressing and configuration commands to the instruments connected.  The commands going across are MTA0, MLA7, DCL, and LLO.

The zoomed in capture clearly showed that NRFD signaled that the listener was ready for data (by the listener), DAV then signaled that the data on the bus is valid (by the talker), and the NDAC signaled that the listener received the data (by the listener).  Because of the handshake, we can tell that the listener definitely received the data. 

Is this setup giving you problems?  If the instrument at Primary Address 0 has data to send, the instrument at Primary Address 7 should be configured to receive that data after MTA0 and MLA7 are sent.

I hope this helps,

Steven T.

Message Edited by Steven T on 05-13-2009 08:52 AM

[WH-Tan]

Hello Steven,

I'm driving the GPIB bus with NAT9914, which in turn is controlled by the uC. It takes almost 2 weeks to progress until this state, and I'm still experimenting with a couple of uncertainties - the hardware, the firmware and the set-up of NAT9914 registers etc. Surely your confirmation is a big help here, as it cuts down some of the uncertainties. Thank you very much. I appreciate it.

Best regards,

Message Edited by WH-Tan on 05-14-2009 01:07 AM

Message Edited by WH-Tan on 05-14-2009 01:08 AM

[rushcom]

Hello WH-tan

i am also using the NAT in the same way uc+nat 9914,& i am not getting any output so can you please guide me with the delay you have set between the the commands