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Connecting to a Remote PLC Controller

Publication ERSC-1008 Rev 1.1 – October 2017

Any Modbus TCP capable PC or PLC can connect to any ConveyLinx-IO visible on its network and access Input and

Output Holding Register Assemblies. ConveyLinx supports the following Modbus TCP Service Codes:

• Service Code 3 - Read Holding Register (up to 45 registers per instruction)

• Service Code 6 - Write Single Register

• Service Code 16 - Write Multiple Registers (up to 45 registers per instruction)

• Service Code 23 - Read/Write Multiple Registers (up to 45 registers per instruction)

When using Input and Output Assemblies with Modbus TCP PLC, it is important to always

use the first address shown in the assembly group as the beginning register to read or

write regardless of which register in the assembly is needed by the PLC. Trying to access

Input or Output Assemblies starting with any register in the assembly other than the first

For more information and open protocol specification, please visit www.modbus.org

ETHERNET I/P ASSEMBLY INSTANCE STRUCTURE

When a ConveyLinx-IO module is attached to an external Ethernet I/P controller (Logix 5000 based PLC, for

example), it is done so as a Generic Ethernet I/O device.

For details on connecting to Rockwell PLC – see Appendix B – Connecting to

Rockwell Ethernet I/P PLC.

Part of this procedure in the PLC is to instruct the Generic device as to which data configuration or instance of

Ethernet I/P the Generic device is to use to report and respond to data to and from the PLC.

From this point forward, it is assumed the reader is familiar with Allen-Bradley Logix

platform addressing notation:

[ModuleName]:O.Data[Index].Bit

[ModuleName]:I.Data[Index].Bit

[ModuleName]:C.Data[Index].Bit

Where:

• ModuleName is the user-defined name of the device

• “O.Data” indicates data written by the PLC to the device

• “I.Data” indicates data read by the PLC from the device

• “C.Data” indicates configuration data sent to the device at initial connection

• “[Index].Bit” indicates the word and bit within the image. If the bit notation is

absent the notation refers to the entire word data type

Pulseroller ConveyLinx-IO User Manual

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