Sub-Ring Diagnostics

Detecting a Sub-ring Break via DRS

This topic describes how to detect a cable break in a on the by diagnosing a DRS.

Step	Action
1	Write a DATA_EXCH block to the DRS managing the sub-ring of interest. NOTE: Use the CPU with Ethernet I/O scanner service to send DATA_EXCH commands to diagnose the status of sub-rings. For other operations (get remote statistics, read data, etc.), we recommend that you send a DATA_EXCH command from a communication module on the local rack.
2	Read the states of ports 5 and 6 on the DRS. The possible port state values are: 1 disabled 2 blocking 3 listening 4 learning 5 forwarding 6 broken
3	If either port 5 or 6 is in a blocking state (2), then the loop is present and healthy (no cable break.) If both ports 5 and 6 are in any other state besides blocking state (2), then there is a cable break on the sub-ring.

This graphic shows breaks in 2 sub-rings connected by DRSs on the . The arrows point to the DRSs, on which you monitor ports 5 and 6 in your application using a DATA_EXCH block:

CPU with Ethernet I/O scanner service on the local rack

BMENOC0301/11 Ethernet communication module (with the Ethernet backplane connection enabled), managing the DIO cloud (7)

main ring

DRS connected to the main ring and RIO sub-rings

RIO sub-ring with a communication break (indicated by an X)

RIO drop (including a BM•CRA312•0 X80 EIO adapter module)

DIO cloud connected to a DRS

NOTE: When you add or remove devices from your network configuration, modify the sub-ring cable break logic in your application.

Writing a DATA_EXCH Block to Diagnose a Sub-ring Break

This is an example of a DATA_EXCH block created in a Control Expert application to read the DRS ports 5 and 6 state.

In the Control Expert application, write a DATA_EXCH block to send an EIP explicit message to the DRS that is managing the sub-ring. This EIP explicit message can be sent via the BM•CRA312•0 module or other communication module that is managing devices in the device network.

NOTE: Use a CPU with Ethernet I/O scanner service to send DATA_EXCH commands to diagnose the status of sub-rings.

To create the DATA_EXCH block, create and assign variables, and connect the block to an AND block. The logic continuously sends an explicit message when it receives confirmation of success or detected error.

Refer to the Explicit Messaging topic in the Modicon M340 BMX NOC 0401 Ethernet Communication Module User Manual for details on using the DATA_EXCH block.

Input Parameters

Create variables and assign input pins. In this example, variables have been created (and named) as described below. (You can use different variable names in your explicit messaging configurations.)

Parameter	Data Type	Description
Address	Array [0...7] of INT	The path to the DRS. Use the ADDM function.
ActionType	INT	The type of action to perform. The setting = 1 (transmission followed by await reception).
Data_to_Send	Array [n...m] of INT

Input/Output Parameters

Create variables and assign input pins. In this example, variables have been created (and named) as described below. (You can use different variable names in your explicit messaging configurations.)

Parameter	Data Type	Description
Management_Param	Array [0...3] of INT	consists of 4 words

Output Parameters

Create variables and assign output pins. In this example, variables have been created (and named) as described below. (You can use different variable names in your explicit messaging configurations.)

Parameter	Data Type	Description
Received_Data	Array [n...m] of INT	the EtherNet/IP (CIP) response