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Old October 15th, 2018, 10:00 AM   #1
bornwild
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1734 ADN Point IO status

Hello all,

We have compactlogix CPU with 1769 SDN scanner. The scanner is connected to two nodes 1734 ADN .Every now and then ADN fails with device error of 78 on SDN scanner. The fault gets clear by removing the connector and resetting it.Can one of the Point IO module fault can led to this. How do I get the status of the POINT IO in Rslogix. GSV will not work as this on the device net network.Please suggest
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Old October 15th, 2018, 02:05 PM   #2
Ken Roach
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The 1734-ADN scans the PointBus backplane and aggregates the I/O module data for exchange with a DeviceNet master. The two sides are isolated.

It's possible for a damaged I/O device or module to "take down" the 1734-ADN, but only if they share power supplies and the problem causes the supply voltage to drop.

You can get the status of the I/O connection between the 1769-SDN and the 1734-ADN in the Scanner's slave status array tag.

The name of that tag will be something like "Local:1:I.Status.DeviceStatus[x]" where the [x] is the Node Number of the 1734-ADN.

Error Code 78 appears when the scanner can't get a configuration message through to the slave device. If you were to watch carefully, it was probably preceded by an error code 72, which is when the I/O connection itself times out.

90% of DeviceNet problems come from substandard or damaged wiring, missing termination resistors, or poor installation practices. Check for loose wires and verify that there are two (and only two) 120 ohm termination resistors in place.
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Old October 15th, 2018, 02:39 PM   #3
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Thanks Ken. I suspect a failed I/O on the 1734 ADN point IO. How can I get the status of the Point IO modules to know which is giving me this Fault. On ethernet i use GSV instruction .How can I do the same on device net.
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Old October 15th, 2018, 02:55 PM   #4
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This is a little trickier. Then 1734-ADN can be configured to report just the raw I/O data, or also to include some status data in its connection.

Look in your RSNetworx project and/or your Studio 5000 project to see how much data is mapped for the Input from the 1734-ADN. If there are two "extra" bytes at the beginning of the Input assembly, those are probably status.

https://literature.rockwellautomatio...m002_-en-p.pdf

Page 2-21 of that User Manual shows the meaning of the bits in those two Status bytes.

Unfortunately that's not enough data to tell you which module on the POINT I/O assembly has failed; it only tells you that there's a problem on the POINT Bus.

To get the exact problem with the exact module, you'll have to use a CIP explicit message to one of the status objects described later in Chapter 2. The Node Status table (Class 0x90, Instance 1, Attribute 0xC) is in the same format as the Node Status table that's created in your CompactLogix tags for the 1769-SDN.

Again, in general a failed I/O module on the POINTBus will not cause a total failure of the 1734-ADN adapter (which will show up as Error 78 on the Scanner).

Ideally, capture as much information as you can about the condition of the 1734-ADN device when it's in this failed mode, including the status of the LEDs on the adapter and on the I/O modules, and what steps need to be taken to recover it.
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Old October 16th, 2018, 03:22 PM   #5
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I really dont know what the problem is as it runs fine for 2-3 days . The 1734 ADN network status goes red. Unplug and plug device net connector and it starts working. Yesterday the customer complained that the cylinder started to move bypassing all interlocks. I checked the analog configuration and i have found fault action was go the low clamp. I really doubt there is some issue with the POINT IO modules
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Old October 16th, 2018, 04:08 PM   #6
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Any chance that cylinder's pneumatic valve is wired to the same DC power supply as the DeviceNet network ? A brown-out or voltage spike is a classic reason for an adapter to declare the network "bus off".
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Old October 17th, 2018, 07:41 AM   #7
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We have replaced the ADN adapter. Let's see
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