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Address Plug replacement

If I have an IS address plug that was mistakenly installed on a non-IS baseplate can I remove it and replace it with the right address plug? I am sure I will lose the signals on the baseplate where the wrong address plug resides but will I lose the signals on any of the other seven baseplates?

Colin Munsey

• 2 Apr 2025 10:49 AM
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2 Replies

• Andre Dicaire

  

  • 2 Apr 2025 3:42 PM

  The Address plugs are designed to be replaced under power, provided you replace with the same address number. Here's what happens.
  
  The address plug provides a regulated voltage to the base plate this determines the address of each slot. When a CHARM is inserted or the CIOC is powered up, each CHARM reads this address and stores its Physical address. The CIOC polls each CHARM position based on this address to commission them. The CHARM responds and receives its configuration from the CIOC, and from that point forward, the address plug is not actively involved in addressing.
  
  If the Address plug is removed, or fails, the affected CHARMs will flag the error. All 12 CHARMs in that baseplate will indicate an issue, flashing their red LED and reporting an integrity issue with the hardware. The CHARM does not know if the Address plug is at fault, but seeing all CHARMs on the baseplate with the same issue confirms the common source.
  
  The CHARMs continue to function and each IO signal remains healthy so there is no impact to control. The Flashing LED in this case indicates a fault that is affecting the integrity of the CHARM, but the issue is perceived to be outside the CHARM, much like a short circuit on the field wiring. The CHARM calls attention to itself, but is indicating the issue is external to it. In this case the Address Plug voltage is missing.
  
  Note that Injected Power applied to the Address plug terminal is unaffected by the Address Plug itself and it can be removed without affecting power diistribution on the baseplate.
  
  When a new address plug is installed, the CHARMs will read the physical derived address and compare this to their stored address. If the address is different, IE, you install a different address number, the CHARMS will continue to indicate an error and reject this as it conflicts with what they know to be correct. Even if you install the wrong address number plug, you are still not going to affect control. Install the matching address plug and the CHARMS will clear the error when the address matches their stored address.
  
  If you are trying to change the address plug to change the address of the CHARMs, you will need to remove these CHARMS in order to reset their internal address to the new physical address determined by the new and different address plug.
  
  What happens if you lose power to the CIOC while the Address plus is removed? The CHARMS on that Baseplate will not be able to determine their address until an address plug is installed. You would lose all signals when the CIOC loses power, and would not regain any CHARMS that cannot determine their address.
  
  Therefore, you must maintain address plugs in the baseplates so that they can recover following a power cycle. Note that redundant power on redundant CIOC mitigates spurious power loss. The addressing persists through Address Plug failure and/or replacement.
  
  Emerson chose to use a hard coded addressing scheme that does not rely on micro switches or other mechanical components that could be affected overtime in corrosive environments or suffer damage when manipulated. Addressing is clearly identified. Also, the order of the baseplate addresses is independent of physical connection order. Normally, an 8 baseplate CIOC installed on a single vertical rail will be addressed sequentially. In a panel where baseplates are installed on two or three vertical rails, or in migration projects where baseplates are installed in four rows of two horizontal baseplates, the Extender Cables paths can be optimized (minimal lengty) but the logical order of the base plate addressing is based on what makes sense to users. 1-2, 3-4, 5-6, and 7-8 with odd on the left, even on the right. or 1-2-3, 4-5-6, 7-8 with 1, 4 and 7 at the top or each collumn. cables can go bottom to bottom, top to top or bottom to top, bottom to top. Addressing doesn't care about cable path. You could even cable differently between primary and secondary, though I would not recommend that approach. My point is addressing is independent of cables.
  
  Yes you can replace the Address Plug on line.

  Andre Dicaire

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• Colin Munsey

  

  • 2 Apr 2025 5:56 PM

  In reply to Andre Dicaire:

  Thank you very much. This is exactly what I needed.

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