Serial bus decoding not as expected

Hello,&#160;<br> I am using an MDO4054B-6 with firmware 3.22 (latest available I believe), with DPO4BND module which includes serial bus analyzer.&#160;&#160;<br> <br> When I decode a 1553 stream, it identifies the Sync, and the RT Address, however the remainder of the command word or status word is just <strong>11 bits that are not decoded</strong>, grouped, or tagged in any manner, followed by the parity bit.&#160;&#160;<br> <br> In a YouTube tutorial video published by Tektronix, I can see the decoder (using MSO4104B) should also be able to identify <strong>the transmit/receive bit, subaddress, and word count.</strong>&#160;Not sure but maybe it can also identify Mode Code.<br> <br> So I gathered a few screenshots of what I am seeing on my scope, and also some of the YouTube video.&#160; Is there some software update I need to make to get the decoding to be more useful like in the video?&#160;&#160;<br> <br> Thanks

Hi Matthew,<br> <br> The decoding seems to be working as expected until it reaches the receive/transmit bit, suggesting the waveform data doesn't match what the instrument expects for the 1553 protocol.<br> <br> I would ask that you post here a waveform file of one of these waveforms that are giving you trouble so I can further help you with this problem.<br> &#160;

Thanks Afonso.&#160;<br> <br> I am attaching following:<br> <br> 1) Screenshot of a captured BC-RT command alone.&#160; The command being sent by my BC is 04-1-16-01 (RT address 4, Transmit, Subaddress 16, one data word). In hex that is 0x2601.&#160;&#160;<br> <br> 2) Screen shot of corresponding Event Table, which correctly shows payload 0x2601.<br> <br> 3) Waveform file (ISF) for the one waveform.&#160; I think there is not a way on the scope to save the corresponding bus signal or event list other than the screenshot.&#160; But if there is a way I can try.<br> <br> &#160;

Hi Matthew,<br> I apologize for the delay.<br> <br> I tried the waveform on one of our MSO4000B's and got the same decoding. Next I tried it on an MSO5 and I got it to decode properly, but only with maximum response time (RT) set to 4.1 us or lower (screenshot attached).<br> I tried setting the maximum RT to below 4.1 us on the MSO4000B but was not able to successfully decode the bus. Further work is needed to understand this issue.<br> <br> I would suggest changing changing the time/div and RT maximum and minimum and seeing how that affects the decoding, it might be possible to make progress that way.

I tried it with a little more data (RT response with one data word).&#160;&#160;<br> <br> If I play with the RT max/min, <em>sometimes</em> I get correct decoding on the RT status word only.&#160; &#160;The BC command never gets decoded no matter what the setting.<br> <br> I played with time/div, amplitude, bus thresholds, and trigger position.<br> <br> Screenshot attached, as well as the additional data.&#160;&#160;<br> <br> I'm trying to understand if this is a bug in the decoder, or if the signal is bad in some way.&#160; Because you said it works fine on MSO5, it makes me think it is the former.<br> <br> <br> <br> &#160;

<p>I wouldn't say it works fine on the MSO5. Yes, I can get it to decode somewhat closer to what you expected but it still throws a sync error at the end.</p> <p>This leads me to believe the waveform itself is somehow misshapen (I don't know enough about 1553 to say how exactly) and the MSO5 simply has a slightly different decoding procedure which I have abused to force it to decode something else. I have attached screenshots with the bus decode table to show that.</p> <p></p> <p>It would be useful to know the minimum and maximum RT of the measured system.</p>