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EtherNet/IP

This document is the User Manual for the Virtual I/O Module (VIM) with the EtherNet/IP communication driver firmware for the Emerson Process Management (EPM) DeltaV Control System; it provides information required to install, configure, and maintain the driver firmware on the VIM. The reader should be familiar with EPM’s DeltaV Programmable Serial Interface Cards (PSIC), Rockwell’s DF1 protocol, and connected field devices (supporting the EtherNet/IP protocol).

Protocol Compatibility

IOD-4102 and IOD-4112 EtherNet/IP implements the protocol as specified in the following documents:

These documents are published by Rockwell.

Theory of Operation

The DeltaV Virtual I/O Module (VIM), together with its dedicated system power supply must be plugged into a 2-module carrier on the left-hand side of the DeltaV controller as shown below. The card is clearly labeled with the interface type as Virtual I/O Module. LEDs, located on the front of the card, show the power, error, and port status of the interface at a glance. This current version of the VIM firmware supports both simplex and redundant communications with field devices.

The VIM provides a native DeltaV I/O interface to open plant Ethernet networks and devices that use the EtherNet/IP protocol. DeltaV controllers can read and write signals from the plant floor devices that use these Ethernet networks such as PLCs, Motor Control Centers, and Weigh Scales. As such, the VIM is a Network Gateway between DeltaV controllers and field devices supporting network communications. Simplex and Redundant connectivity is illustrated below:

Figure 1 - Simplex EtherNet/IP Network

Figure 2 - Redundant EtherNet/IP Network

The Virtual IO Module with the EtherNet/IP Driver provides the following compatible functions using the Control and Information Protocol (CIP) as defined in release 1.0 of the EtherNet/IP specification from Open DeviceNet Vendor Assoc. (ODVA) & ControlNet International.

  1. UCMM (unconnected) messaging – Encapsulated DF1 to PLC5, SLC and ControlLogix devices. These messages are initiated from the VIM, in a command /response format. For PLC5 and SLC devices, the VIM reads/writes the configured native tables directly. For Logix devices, user must create PLC5/SLC table mapping to Logix Controller Tags. This is done using Rockwell RsLogix software when programming the Logix device.
  2. Class 1 (I/O) connection. The VIM communicates with ControlLogix devices using the generic 1756-ENBT format. Generic 1756-ENBT modules are configured in the I/O configuration section of the Logix device. Each ENBT corresponds to a VIM dataset. This functionality is available in simplex VIM architecture only. This is because when using the generic 1756-ENBT communication mechanism, the VIM dataset behaves as a slave to the ControlLogix PLC.

Note that the type of messaging used is application dependent. In some cases, an application may have a mixture of both types within the same system.

DeltaV Native I/O

The VIM provides a native DeltaV I/O interface by emulating four Programmable Serial Interface Cards (PSICs). By design, the VIM acquires the last 8-wide I/O carrier of a DeltaV system, emulating cards 57-60 or 61-64 as a single, simplex unit. Installing 2 simplex VIMs side-by-side provides emulation of all 8 serial I/O cards 57-64. The configuration of card group 57-60 or 61-64, and network properties of connected field devices is done in VIMNet Explorer.

For redundancy support, the appropriate firmware (v 3.3.50 or later) must be flashed into the VIM. Four redundant PSICs are emulated when 2 VIMs are installed side-by-side and configured as a redundant pair. One VIM emulates all odd numbered serial cards, while the other VIM emulates all even numbered serial cards. The emulated serial cards behave as redundant pairs, i.e., 57/58, 59/60, etc. However, when redundancy switchover occurs, all cards behave as a bank and switch in unison. For example, if there is a communication error on card 57 that requires a switchover, the VIM will switch to its partner and cards 58, 60, 62 and 64 will become active.

The emulated serial cards appear to DeltaV as real serial I/O. The configuration of data tables to be read and written is done at the DeltaV Explorer level, in the same manner as required for a serial DF1 PLC device. This allows communications with any PLC or non-PLC device that supports the EtherNet/IP messaging.

Each PSIC has 2 ports configured under it. There are 16 datasets under each port. Consequently, the VIM has the capacity of 128 datasets. One dataset is equivalent to 100 16-bit registers, or 50 floating point (32 bit) registers. These 128 datasets are user mapped to PLC devices as required for your application.

PLC Devices

The PLC device address is considered unique in the serial cards port domain. Specifically, within a serial port, all configured devices are unique. The user can, however, configure the same device with the same address under another port. For a device address configured more than once under more than one port, the IP address always remains unique.

The VIMNet Server configuration correlates each unique PLC device address with an IP address. At the simplest level, each PLC device equates to an IP address. In some cases, a single IP address may also be mapped to more than one PLC device, as is typically required when interfacing with Motor Control Centers. In this case, the IP address mapped belongs to a gateway device, which in turn acts as a data concentrator communicating serially with multiple actual PLC devices, each with a unique address.

The System Specifications give the maximum number of network devices the VIM supports. Messages for each dataset are concurrently handled by the VIM, thus increasing throughput. The timing of a single dataset does not affect the other datasets. This is particularly useful when a single dataset has errors, or has a high response time.