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Connecting DeltaV to Allen Bradley PLCs via EtherNet/IP VIM
By Adisa Shaljani
Product: DeltaV Virtual IO Module - VIM2

The following article provides details, requirements and options when connecting EtherNet/IP VIM to Allen Bradley/Rockwell PLCs.

There are two types of VIMs: Rockwell PLC EtherNet/IP firmware (IOD-4112), and ODVA EtherNet/IP firmware (IOD-4116). This KBA applies to both.

Question: With which AB PLCs can EtherNet/IP VIM interface?

Answer:The EtherNet/IP VIM can interface with most recent AB PLCs that support EtherNet/IP communications.

The compatible PLCs and their integration modules are shown in the Table 1.

Table 1

AB PLC

Direct Connection

via onboard Ethernet port

Indirect Connection via

external attached or connected card/module

PLC5/XX

Yes for PLC-5/20E, 5/40E, 5/80E

Via attached 1785-ENET side card

SLC 5/05

Yes

Via 1761-NET-ENI module connected to CH0 port.

SLC 5/04, SLC 5/03

No

Via 1761-NET-ENI module connected to CH0 port.

MicroLogix 1000 and 1200

No

Via 1761-NET-ENI module connected to CH0 port

MicroLogix 1500

No

Via 1761-NET-ENI module connected to CH0 or CH1 port

CompactLogix

Yes - CompactLogix model dependent

Via 1761-NET-ENI module connected to CH0 port

Via attached 1768-ENBT or equivalent module.

ControlLogix

No

Via 1756-ENET, 1756-ENBT, or equivalent card in chassis

Question: What are the hardware requirements for AB PLCs to interface EtherNet/IP VIM?

Answer: Three options exist as follows:

  1. The PLC may have an Ethernet port directly on the CPU (which supports EtherNet/IP). The VIM can directly connect to this port.
  2. The PLC may require an attached or chassis resident module. The attached module provides an Ethernet port supporting EtherNet/IP. Also see note below.
  3. The PLC only has a serial DF1 compatible port available. An external EtherNet/IP to serial DF1 converter module must be used as the connection method.

Note: Rockwell PLC EtherNet/IP (IOD-4112) supports communications to ControlLogix using 1756-ENET/1756-ENBT card only if the card is installed in the same chassis as the CPU. If the card is in a separate chassis the VIM will not be able to communicate with the PLC. ODVA EtherNet/IP (IOD-4116) supports extended paths required to have the Ethernet card in a separate chassis.

Question: What are the firmware requirements for AB PLC 5/XX to support EtherNet/IP protocol?

Answer: The PLC5/XXE controllers that have onboard Ethernet port must be at certain revision level to support EtherNet/IP communications. The following table shows the PLC5/XXE processor firmware revisions that are EtherNet/IP compatible. This information was excerpted from Rockwell Publication 1785-6.2-RN1.

Table 2

Series

Revision

Processor

E

D.2 or later

PLC-5/20E

PLC-5/40E

PLC-5/80E

D

E.2 or later

PLC-5/20E

PLC-5/40E

PLC-5/80E

C

N.2 or later

PLC-5/20E

PLC-5/40E

PLC-5/80E

Question: What are the firmware requirements for AB SLC 5/05 to support EtherNet/IP protocol?

Answer: According to Rockwell Publication 1747-10.4 SLC-5/05 controller has to be 1747- L551 or later (series A, B, or C). The processor needs to support the EtherNet/IP messaging protocol as well as the older "CSPv4" messaging protocol. The SLC-5/05 operating system must be OS501 FRN 5 or later (the current firmware is FRN10). The table 3 below shows the different SLC controllers and supported communication ports.

Table 3

Controller No.

No. of Local I/O Chasis, Max.

No. of I/O Module Slots in the Local I/O Chasis, Max.

Communication Ports

SLC 5/01 Processor

1747-L511

3

30

DH485

1747-L514

SLC 5/02 Processor

1747-L524

3

30

DH485

SLC 5/03 Processor

1747-L531

3

30

DH485

1747-L532

RS232

1747-L533

SLC 5/04 Processor

1747-L541

3

30

DH+

1747-L542

RS232

1747-L543

SLC 5/05 Processor

1747-L551

3

30

Ethernet

1747-L552

RS232

1747-L553

Question: What protocol message types are supported in EtherNet/IP VIM to various AB PLCs?

Answer: The two supported messaging mechanisms are UCMM (using Encapsulated DF1 or Tag Access) and Class 1. For more details on supported messaging by PLC see Table 4.

Table 4

AB PLC

Supports Encapsulated DF1 Messaging

Supports Tag Access

Supports Class 1 Messaging

PLC5/XX

Yes

No

No

SLC 5/XX

Yes

No

No

MicroLogix

Yes

No

No

CompactLogix

Yes

Yes

Yes

ControlLogix

Yes

Yes

Yes

Question: What data types are supported by VIM?

Answer: Encapsulated DF1 (UCMM) messaging allows user to read/write the following data types: Boolean, floating point, 16-bit integer and strings. Class 1 messaging allows user to read/write the same data types supported by encapsulated DF1 messaging. In addition, 32-bit integers and ENBT I/O Tag level data can be communicated. Table 5 details the various data types.

Table 5

Data Type

PLC 5/XX

SLC 5/XX

MicroLogix

ControlLogix/CompactLogix

16 bit INT

Yes

Yes

Yes

Yes

Boolean

Yes

Yes

Yes

Yes

Discrete

Yes

Yes

Yes

Yes

Floating Point

Yes

Yes

Yes

Yes

Strings

Yes

Yes

Yes

Yes

32- bit DINT

N/A

N/A

N/A

Yes

ENBT I/O

N/A

N/A

N/A

Yes

Question: Does the VIM support Redundancy?

Answer: Both the Rockwell PLC EtherNet/IP (IOD-4112) and ODVA EtherNet/IP (IOD-4116) firmwares support redundancy.

For Rockwell PLC EtherNet/IP (IOD-4112) redundancy is supported only when VIMs are configured to use Encapsulated DF1 (UCMM) messaging. This means that 32-bit Integer and ENBT I/O Tag level data is not supported by redundant VIMs. The reason for this limitation is that 32-bit integer data types are not supported by Rockwell as part of the DF1 messaging. And when using Class 1 messaging to communicate ENBT I/O Tag level data, the VIM must behave as the Class 1 Target, while the PLC behaves as the Class 1 Originator. Consequently, it is not compatible with supported redundancy mechanisms.

For ODVA EtherNet/IP (IOD-4116) all messaging types are supported in both simplex and redundant modes.