I have a DCS instruction set up for an Emergency Stop (E-STOP) with both restart and cold start types set to automatic. Testing the E-STOP shows it functioning correctly, but after a power failure, the instruction fails to reset. While Channel A and B show a status of 1, the CombinedInputStatus remains at 0. By removing the "01" bit from the DCS, the reset is successful. Attached is a snippet for reference. Can anyone assist in explaining why the CombinedInputStatus is not updating its state?
The Combined Input Status is a crucial status bit on the safety input card, representing the status of all inputs on the card. If any of the inputs are faulted, including those not directly related to the wired e-stop, the status will be off. It is possible that there are other components wired to the card that will remain in error until the e-stops are reset.
Thank you for your response, it now clarifies things for me. I mistakenly believed it only tracked the status of the input used in the instruction.
Based on your provided snippet and the issue you're facing, it seems like there might be a problem with the coding of your DCS. The CombinedInputStatus failing to update might be attributed to timing issue which could be resolved through the addition of a time delay, allowing each channel to fully process their changes before updating the CombinedInputStatus. Alternatively, it could be possible that the reset command is not being sent fully or correctly to all channels. I would suggest double checking third party libraries if any are in use, as sometimes they can have dependencies that interfere with this sort of function. Be sure to look into the PLC reset procedure as well, to verify if the procedure is being followed correctly.
I suspect there might be an issue with the way the power failure is being handled by the system. It could be that after a power outage, there is a status check procedure that is terminated or not initiated correctly. This might result in the CombinedInputStatus not being updated or reset. In normal E-STOP scenarios, the necessary signals to reset CombinedInputStatus are likely still intact, so the problem doesn't surface. You may want to investigate the programming related to power recovery functions. You could also try to simulate a power failure scenario to test this hypothesis and verify the component behaves as expected.
It sounds like the issue might be related to the sequence of power restoration after the failure. The CombinedInputStatus might remain at 0 if the DCS is trying to update its status before all the related systems are back online after a power outage. Essentially, it's hitting a checkpoint before everything else is ready. I had a similar issue with one of my setups, and I solved it by delaying the DCS status update until a confirmation that all interconnected systems were operational. I recommend you check your power restoration sequence or consider adding a delay in the system restart command after a power failure.
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Answer: Answer: The CombinedInputStatus may not be updating its state due to a potential issue with the "01" bit in the DCS instruction. Removing this bit has been reported to successfully reset the instruction after a power failure.
Answer: Answer: To troubleshoot this issue, you can start by checking the settings for Channel A and B, ensuring that they are correctly configured for automatic restart and cold start. Additionally, reviewing the logic related to the CombinedInputStatus and the impact of the "01" bit on its state can provide insights into the reset failure.
Answer: Answer: The discrepancy in the behavior of the E-STOP functionality between testing and post-power failure reset may be attributed to specific conditions related to the DCS instruction setup, such as the handling of the "01" bit and its impact on the CombinedInputStatus. Further analysis of these factors can help identify the root cause of the issue.
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