Allen-Bradley 2085-ECR Micro800 Bus Terminator Module

The end cap for Micro800 expansion I/O

The Allen-Bradley 2085-ECR is the bus terminator module of the Micro800 family. Rockwell Automation describes it as an end cap that terminates the end of the serial communication bus. It is required whenever an expansion I/O module is connected to a Micro800 controller, and it belongs on the last expansion I/O module of the system.

The module is only 15.6 mm wide and weighs about 50 g, so it adds almost nothing to the width of the controller and I/O stack. Without it, the expansion bus is left unterminated, so include one 2085-ECR in every Micro800 order that contains expansion modules, and a conformal-coated 2085-ECRK where the application calls for it.

Technical specifications

How it is used

The Micro800 expansion I/O modules attach to the controller or to another I/O module with interconnecting latches and hooks and a bus connector. The installation instructions for the 2085 input modules state that the controller and the expansion I/O modules must terminate with a 2085-ECR. Lock the module interconnect latches, and tighten the removable terminal block hold-down screws, before applying power.

Do not unlatch the interconnecting latches or remove modules with power on, because an electric arc can occur, which can cause an explosion in a hazardous location installation.

Environment and approvals

The equipment is intended for Pollution Degree 2 industrial environments, overvoltage Category II and altitudes up to 2000 m without derating. It is supplied as open-type equipment for indoor use and must be mounted in a suitable enclosure with a 5VA flame-spread rating if non-metallic. The North American temperature code is T6, and the printed approvals include cULus, CE, RCM, KC and UKCA.

Why a Micro800 expansion bus needs a terminator

Micro800 expansion I/O modules communicate with the controller over a serial bus that runs through the bus connectors of each module in the stack. A serial bus behaves best when its far end is properly closed: without termination, signals reflect from the open end and the controller cannot reliably identify or exchange data with the modules. The 2085-ECR provides that closure, which is why Rockwell Automation lists it as required rather than optional whenever expansion I/O is present. A system that uses only the base controller and plug-in modules, with no 2085 expansion I/O, does not need an end cap.

Key points for designers and panel builders

• One per system: a single 2085-ECR closes the bus after the last expansion module, regardless of how many modules sit between it and the controller.
• Narrow footprint: the slim width keeps the overall stack compact on the DIN rail or panel.
• Same latch system: it uses the interconnecting latches and hooks already used by the expansion modules, so no separate tools or fixings are needed.
• Coated option: the 2085-ECRK variant is the conformal-coated version for harsher atmospheres, with the same specifications.
• Negligible heat: its power dissipation is so small that it does not affect the thermal design of the enclosure.

Choosing between 2085-ECR and 2085-ECRK

The standard 2085-ECR suits clean control rooms and air-conditioned panels. Conformal coating protects printed circuit assemblies against moisture, condensation and some airborne contaminants, so the 2085-ECRK makes sense when the rest of the Micro800 system is also ordered in K (coated) versions, for example in water and wastewater plants, coastal sites or areas with corrosive gases. Mixing a coated controller and coated I/O with an uncoated end cap leaves one part of the bus less protected than the rest, so order the coated end cap alongside a coated system.

Installation and handling tips

Plan the module order before mounting: expansion modules are added to the right of the controller and the end cap always goes last. When a module is added later, remove the end cap with power off, latch the new module, then refit the end cap on the new last module. Check that both front and rear latches have clicked fully home, since a partly engaged latch can give an intermittent bus connection that is hard to trace during commissioning.

The terminator is open-type equipment and must be inside a suitable enclosure, together with the controller and I/O. In hazardous locations follow the Class I Division 2 instructions printed in the installation documents and never separate modules under power. During maintenance, keep a spare end cap in stock: if it is lost or damaged when a panel is modified, the expansion I/O cannot be used until a replacement is fitted.

Where it is used in Oman and the GCC

Micro800 controllers are popular on small machines, packaged pumps, HVAC units, lift and gate controls, irrigation and small water treatment skids across the region. Each of those systems that carries 2085 expansion modules needs its own 2085-ECR. OEMs building several identical panels often order the end caps together with the controllers and I/O so that every panel leaves the workshop complete.

What to include in an RFQ

• Catalog number 2085-ECR or 2085-ECRK and the quantity.
• The Micro800 controller and expansion modules in the same system, if you would like them quoted together.
• Whether conformal coating is a project requirement.
• Any certification needs for the site, such as hazardous location approval.
• Delivery location in Oman or elsewhere in the GCC.

Documents and quotation

The Rockwell Automation Micro800 bus terminator installation instructions, publication 2085-IN002, are attached. See our automation accessories catalogue and PLC and I/O cards for Micro800 expansion modules. Confirm the exact catalog number, series letter and firmware or hardware revision on the product label, and the compatibility with your existing system, before ordering. Stock and lead time are confirmed at quotation.