Overview

The topic describes the attributes that you can configure to obtain diagnostic data when system monitoring is enabled.

The DIAGNOSTIC tab is available for generic automation devices that communicate by using Modbus TCP and that are capable of providing diagnostic data based on requests that are sent to the device. It lets you view and configure the services that you want to monitor.

Description of Attributes

Attribute

Default value

Description

Presence

True (selected)

When selected, enables sending requests to the device in order to display a diagnostic icon, which indicates the communication status of the device.

NOTE: The Service not available (gray dot) icon is displayed by default when Presence is cleared.

Protocol

Ping

Protocol that is used to send requests to the device to obtain its communication status.

Request Code

Blank

The request that is sent to the device to obtain diagnostic data including the data address to be read. The request is protocol and device specific.

Format: Byte array using decimals, comma separated, without spaces, in brackets.

Example:

For a Modbus request to read the content of analog output holding registers 40108 to 40109 from the device with address 17 which is

11 03 006B 0002 7687

Where:

  • 11 is the hexadecimal slave address

  • 03 is Function Code 3

  • 006B is the address of the first register to read (decimal 107 with 4001 offset)

  • 0002 is the number of registers to read

  • 7687 is the cyclic redundancy check (CRC)

Enter the following: [17,03,00,107,00,03,118,135]

Operating State Subcategories

Each subcategory corresponds to an operating state that can display the corresponding diagnostic icon. More than one icon can be displayed at the same time for a device.

To configure these attributes, Presence must be enabled.

The table describes the set of attributes that are available for each operating state.

Attribute

Default value

Description

Enabled

False (cleared)

When selected, enables sending requests (Request Code ) to the device in order to display the corresponding operating state icon based on the result of Request Expression.

Protocol

Modbus TCP

Protocol that is used to send requests to the device to obtain its operating status.

Read-only.

Request Expression

Blank

Logical expression, which is applied to the reply that is received from the device for Request Code. When true, the software displays the corresponding operating state icon.

The expression is device-specific.

Example:

If the reply to the above request code example is

11 03 06 AE41 5652 4340 49AD

you can enter:

  • [4]=174 to check the high value of register 40108 (hexadecimal AE is 174)

  • [4].0 to check bit 0 of byte 4

Syntax example:

LEN>3 AND ([1]=0 OR [1]=2)

You can use operators AND, OR, and NOT and the following functions.

Function

Description

[ByteIndex].BitIndex

Specifies the bit in the byte at ByteIndex, which is the offset of the byte in the reply.

[ByteIndex]=value

Checks if the value of the byte is equal to value.

[ByteIndex]!=value

Checks if the value of the byte is different from value.

LEN>value

Checks if the length of the reply is greater than value.

LEN<=value

Checks if the length of the reply is smaller than value.