products

The PACSystems* Redundancy Memory Xchange (RMX) module operates as a node on a reflective memory network or as a dedicated link between CPUs in an RX3i Hot Standby CPU Redundancy system. When the RMX is not being used as a link in a redundancy system, it is functionally identical to the IC695CMX128 module. Each node in the network can be any reflective memory device that is compatible with the 5565 family. Whenever data is written to one node, all nodes on the network are automatically updated with the new data. When used as a node on a reflective memory network, the RMX module provides deterministic sharing of data among PLCs and other computing devices on a high-speed fiber optic network. A reflective memory network can contain up to 256 nodes. Each node in the reflective memory network is connected in a daisychained loop using fiber optic cables. The transmitter of the first node is tied to the receiver of the second. The transmitter of the second node is tied to the receiver of the third node, and so on, until the loop is completed at the receiver of the first node. When used in a CPU redundancy system, the RMX modules provide a path for transferring data between the two redundancy CPUs in the redundant system. A complete communications path consists of one RMX in the primary unit, one RMX in the secondary unit, and two highspeed fiber optic cables connecting them to each other. This must be a two-node ring: no other reflective memory nodes are allowed to be part of this fiber optic network. GE Intelligent Platforms strongly recommends two redundancy links (a total of four RMX modules) be configured and installed. Optionally, systems can be configured for a single redundancy link (a total of two RMX modules). When the RMX is being used as link in a redundancy system, it cannot be used as a general-purpose Memory Xchange module. For details on the operation of a PACSystems CPU redundancy system, refer to the PACSystems Hot Standby CPU Redundancy User’s Manual, GFK-2308. A PACSystems RX3i main rack supports a maximum of six Memory Xchange modules in any combination of RMX128 and CMX128 modules. A maximum of two RMX modules can be configured as redundancy communication links.