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gromit

SLC5/04 link issues (1770-KF2)

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Trying to add points to a QLC link from WDPF to SLC5/04, incorporating a 1770-KF2 DH+ interface module. This link has been in place for years, incorporating only DCS reads (both digital and analog). We recently added several more DCS reads successfully, but cannot seem to get digital or analog DCS writes to be seen by the registers in the SLC5/04 data table. Could this be a limitation by the 1770-KF2 module, or is there a more probable reason? SLC5/04 DH+---------1770-KF2---------QLC Could Duplex settings on the 1770-KF2 module have a bearing on this dysfunction? Successful DCS analog reads PT101, N9:2, A0000 PT102, N9:3, A0002 DP103, N9:4, A0004 Unsuccessful DCS analog writes PV101, N9:18, A0500 PV102, N9:19, A0502 PV103, N9:20, A0504 Any insight would be greatly appreciated. Thanks.

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The only way to be certain about what's going on is to capture and analyze the DF1 traffic on the serial link. It's almost certainly not the duplex or serial framing settings; those would have caused trouble with Read instructions too. Does the WDPF give you any sort of error code, or do you just fail to see the data change in the SLC ? Is it possible that something in the SLC-5/04 logic is writing over those memory locations ? Are you sure that the N9 file is not Read-Only ? In RSLogix 500, examine the Data File properties to see if either the "Constant" or "Static" radio buttons are selected under "Protection".

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Wow Ken, lot's of stuff to consider. Please find my response below in bold blue font. The only way to be certain about what's going on is to capture and analyze the DF1 traffic on the serial link. Why would I monitor the DF1 traffic if I am using the dedicated 1770-KF2 module? It's almost certainly not the duplex or serial framing settings; those would have caused trouble with Read instructions too. Understood, but I had to ask. Does the WDPF give you any sort of error code, or do you just fail to see the data change in the SLC ? There is no error code provided...just the absence of the write data exchange in the SLC. Is it possible that something in the SLC-5/04 logic is writing over those memory locations ? Good idea but I checked, by typing a value in the data table to confirm it was not being overwritten. Are you sure that the N9 file is not Read-Only ? In RSLogix 500, examine the Data File properties to see if either the "Constant" or "Static" radio buttons are selected under "Protection". I have never seen any case where a data file was write protected, but I will look into it first thing tomorrow morning. If the data file is write protected, will I be able to change the value within the data table or not? I hope this is the issue, because I can't think of anyhing else. Thanks...I will report findings in the morning.

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I couldn't wait till morning. I looked at the properties of the N9 data file... and the constant and static radio buttons were not selected under the protection category, rather, the none option was selected. I took a snapshot of it, but don't know how to attach it. Any other ideas?

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It's fairly easy to capture and analyzer DF1 Full Duplex traffic, but analyzing DH+ requires much more expensive and complex hardware and software. It's possible that the DCS is sending the commands correctly, and the KF2 is receiving them correctly, and that the problem is on the SLC-5/04 side. It's also possible that the DCS is making a mistake; wrong function code, wrong data file, something. Or it's getting and error response and not providing an indication of that error response. Thanks for checking the data file write protection; if it's set to "None" that means that it can definitely be written to by the DH+ port.

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Thanks Ken. Soooo, what is the best next step to troubleshoot and resolve the dysfunction???

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Want to borrow a Stratus Engineering EZ-Tap ? That's going to be the easiest and most cost-effective way to capture the DF1 Full Duplex traffic, especially if you happen to have a 9-pin D-shell connector set somewhere in the system. PM me with a shipping address and you can use mine.

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Ken, That is incredibly generous of you to offer your Stratus Engineering EZ-Tap. Before I accept your offer please clarify the following, so as not to waste time or efforts. Per the attached pics and rudimentary schematic below, the “blue hose” connects the top DH+ port to the 1770-KF2 module. SLC5/04 DH+---------1770-KF2---------QLC So will interrogating the DF1 port via the Stratus Engineering EZ-Tap offer any insight, if the link is going through the DH+ port? ...I still can't figure out how to attach a file to a post.

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The 1770-KF2 has a 25-pin RS-232 port, so that's going to connect to the QLC. If the QLC has a 9-pin RS-232 port, the EZ-Tap can go there directly. If it has a 25-pin connector or some other connector, you're going to need a pair of 25/9 pin adapters. The QLC has to be talking DF1 to the 1770-KF2, which translates those frames to DH+ protocol. The data payload is almost the same; it's the "PCCC" command set.

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Thanks Ken. I'm gonna ask my colleagues if they have the EZ-tap or similar device, before imposing on you. Is the EZ-tap software user friendly, especially with respect to Allen Bradley protocol? Is the software rich enough to identify the possible cause of the missing DCS writes?

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EZ-tap and its utility software are a great value, but they are a raw data collector rather than a protocol analyzer. The best protocol analyzer for industrial serial protocols is Frontline Test Equipment's NetDecoder. That's what I used when I did this sort of thing for a living. In your case, you're not looking for an intermittent problem, so decoding the DF1 protocol packets by hand shouldn't be too hard as long as you've got a good separation between Transmitted and Received data, which is something that EZ-Tap does very well.

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Ken, I found out that my colleague did not have the EZ-tap and its utility software. However, my boss gave me permission to purchase a sniffer device for troubleshooting such as this. Is the Stratus Engineering EZ-Tap the best device that you can think of or would you suggest a better option within the $100 to$200 cost range? Looking on the http://www.stratusengineering.com/EZTap.html website, they have two choices. 1: EZ-Tap™ RS-232 Passive Tap Module for $160.2: EZ-Tap Pro™RS-232 Passive Tap Module - Bus Analyzer / Protocol Analyzer for $290.Which would you suggest, and do you know of any other place to purchase them at a discounted price? Thanks.

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The 1770-KF2 wasn't capable of any speeds higher than 19200 baud, so you just need the ordinary EZ-Tap. I have one of those plus a Versa-Tap, the RS485 version. In my opinion the EZ-Tap is a great value. When they first came out I sent them as Christmas presents the the guys who helped me with serial comms projects !

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