Redundancy Memory Xchange (RMX) Module

The Redundancy Memory Xchange (RMX) module functions either as a node on a reflective memory network or as a dedicated communication link between CPUs in a redundant PACSystems RX7i system.

When the RMX module is not used as a redundancy link, it is functionally identical to the IC698CMX016 Memory Xchange module. In this mode, it participates in a reflective memory network where all compatible nodes automatically share data in real time.

Reflective Memory Network Operation

In a reflective memory network, each node can be any reflective memory device compatible with the VMIC 5565 family. When data is written to the memory of one node, the update is automatically propagated to all other nodes on the network with deterministic timing.

Key characteristics include:

Deterministic, high-speed data sharing among PLCs and other computing devices

Fiber-optic communication for noise immunity and high reliability

Support for up to 256 nodes per network

Network Topology

Nodes are connected in a daisy-chained fiber-optic loop

The transmitter of each node connects to the receiver of the next node

The loop is completed by connecting the last node back to the first

CPU Redundancy System Operation

When used in an RX7i Hot Standby CPU redundancy system, RMX modules provide the communication path for transferring memory data between the primary and secondary CPUs.

A complete redundancy communication path consists of:

One RMX module in the primary unit

One RMX module in the secondary unit

Two high-speed fiber-optic cables connecting the modules

This configuration must form a dedicated two-node ring. No other reflective memory nodes are permitted on this fiber-optic network.

Redundancy Link Recommendations

GE Fanuc strongly recommends configuring two redundancy links, requiring a total of four RMX modules

Systems may optionally be configured with a single redundancy link (two RMX modules)

When configured as a redundancy link, the RMX module cannot be used as a general-purpose Memory Xchange module.

For detailed redundancy operation, refer to the
PACSystems Hot Standby CPU Redundancy User’s Manual (GFK-2308).

System Configuration Limits

A PACSystems RX7i main rack supports up to four Memory Xchange modules, in any combination of RMX016 and CMX016

A maximum of two RMX modules may be configured as redundancy communication links

Features

Single-slot PACSystems RX7i form factor

16 MB reflective memory with parity

Fully software-configurable node parameters (no jumpers or switches required)

High-speed 2.12 Gbaud fiber-optic network

Operates independently of RX7i CPU processing

Compatible with VMIC 5565 family reflective memory devices

Supports multimode fiber connections up to 30.48 m (100 ft)

Dynamic packet sizing, automatically managed by the Memory Xchange module

Programmable VMEbus interrupt output

Four general-purpose network interrupts, each with 32 bits of data

Network error detection

Supports up to 256 nodes per network

Optional redundant transfer mode, reducing the probability of dropped data packets

Configurable network memory offset, allowing assignment of nodes to specific 16 MB address segments