Rockwell Automation Software/RSLinx

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RSLinx Classic is an inclusive communication server which provides plant-floor device connectivity for a wide variety of Rockwell Software applications such as

  • RSLogix 5/500/5000
  • RSView32
  • FactoryTalk View Site Edition
  • FactoryTalk Transaction Manager

Besides, numerous open interfaces are provided for third-party HMI, data collection and analysis packages, and custom client-application software. RSLinx Classic is capable enough to support multiple software applications at the same time, communicating to a range of devices on many different networks.

RSLinx Classic 2.x is now associated to RSLinx Enterprise, a new product that provides supreme connectivity to Logix processors. RSLinx Enterprise provides data services for distributed FactoryTalk View Site Edition products, FactoryTalk Transaction Manager, FactoryTalk Historian, and FactoryTalk Metrics applications.

One can communicate from anywhere to anywhere using RSLinx Classic. RSLinx is available in multiple packages to meet the demand for a variety of cost and functionality requirements.


Major RSLinx benefits include:

  1. Routing: RSLinx Classic 2.x provides a user-friendly graphical interface for navigating through our network. This includes routing over an office Ethernet network through a ControlLogix Gateway to get to our control networks and devices on the plant floor.
  2. Graphical Interface: RSWho is the network browse interface providing a single window to view all configured network drivers. The multi-pane window allows navigation through network hierarchy in the left pane while RSWho displaying device icons along with their status in the right pane.
  3. Data Table Monitors: RSLinx can be used to view data values in a PLC-5, SLC-5, MicroLogix, or ControlLogix processor. For RSLinx Data Table Monitor a PLC-5 / SLC-5 / MicroLogix device, select a data table file to view from a list of available data table files in the controller. For a ControlLogix processor, view tag information in a hierarchical list as the tags are defined in the target device. Multiple data monitor windows can be displayed at the same time providing an effective trouble-shooting tool. Data Monitor functionality is only available with RSLinx Professional and FactoryTalk Gateway.
  4. Ladder Viewers: RSLinx includes an extremely valuable Ladder Viewer for PLC-5, SLC-5, or MicroLogix controller. Based on the RSLogix family of programming software, it allows viewing of the ladder code including symbols, address descriptions and rung comments for an effective and complete diagnostic tool when used on your HMI or data collection station on the production floor. Ladder Viewer functionality is only available with RSLinx Professional and FactoryTalk Gateway.
  5. Remote OPC: RSLinx and FactoryTalk Gateway extend communications throughout the enterprise. RSLinx clients such as RSLogix 5/500/5000 can connect over Ethernet through an RSLinx and FactoryTalk Gateway and impeccably go online to a PLC-5, SLC-5, MicroLogix, or ControlLogix processor residing on a control network accessible by the gateway machine. Another key usage of RSLinx and FactoryTalk Gateway is to optimize communications between multiple OPC clients and plant floor devices. The benefit of using RSLinx Gateway is that overlapping data requests from multiple clients are consolidated into one request to the controller thus reducing the overall network traffic and burden on the targeted controller. From a cost perspective, you no longer need a copy of RSLinx running on each client machine.
  6. Open Interfaces: RSLinx provides connectivity for client applications using OPC or DDE. OPC is the preferred interface for data acquisition applications because it is the Defacto standard for factory communications.

OLE for Process Control (OPC)

OPC is based on Microsoft's OLE technology and is defined and managed by the OPC Foundation (a coalition of industrial/manufacturing companies of which Rockwell Software is a prominent member). The charter of this group is to provide an industry-standard exchange mechanism optimized for OPC performance. RSLinx is an OPC Data Access 2.0 compliant server which provides an OPC custom interface for C/C++ client applications and an OPC Automation interface for VB/VBA client applications. The added benefit provided from RSLinx is its ability to provide several DDE formats in addition to OPC and its DDE/OPC diagnostic information.

Data Collection Modes

In RSLinx, we create a DDE/OPC Topic as a named alias to a targeted device. This alias name is used while requesting data in a client application through the OPC or DDE interfaces. Each topic has parameters to specify poll rate, communication timeout, and the data collection mode. Two data collection modes are discussed below:

Polled mode: In this mode, RSLinx performs all of the work and hence it is easy to make changes and control the communications. Polled mode does however add to the CPU usage on the PC since RSLinx is constantly polling and increases the communication traffic volume compared to unsolicited mode.

Unsolicited mode: In this mode, data is sent to RSLinx by a message instruction in the processor. RSLinx waits for a packet from the processor instead of polling. The advantage of this mode is that communication traffic is typically reduced due to the controller determining how often to send the data. Unsolicited mode is a good method of transferring large amounts of data that changes infrequently like when a product or batch completes and the record data needs to be transferred to the client. The disadvantage is that unsolicited mode requires ladder programming to gather and send the data.

Diagnostic Tools

RSLinx includes a wealth of diagnostic information to assist us in analyzing our system. Whether it's trouble-shooting a communication problem or analyzing network throughput, RSLinx provides the needed information. Diagnostics fall into following three major categories:

  1. Networks: Diagnostic counters track server information such as messages sent, messages received, messages acknowledged, communication errors, and timeouts. Performance counters give throughput in terms of packets/second.
  2. Station: Diagnostic counters indicate information for a selected station such as messages sent and received, message retries, and packet errors.
  3. OPC/DDE: Multiple dialogs for DDE clients, OPC Groups, Optimized Packets, and OPC/ DDE server connections display diagnostic information specific to the category. A Communication event log displays information specific to an OPC/DDE transaction.