The Item Statistics display shows statistics for the selected OPC item. The number of transmits, receives, and errors are displayed for the selected item. Other available statistics include the last time the driver successfully read data from and wrote data to the item, the OPC quality of the item, the server’s native data type, and the access rights for the item.
To display an item’s statistics, select the item in the Tree Browser and then choose Stats Mode from the Display Mode menu.
The following describes the fields and buttons that are visible in the Item Properties Viewer in Stats Mode:
Item ID
Specifies the fully qualified ID for this item and describes the properties of the data point that you want to read. For example, an item ID can contain addressing parameters, engineering units, and scaling properties.
Valid Entries
The format of the item ID is specific to each OPC server. Refer to your OPC server documentation for more information.
If your OPC server supports browsing, you can click the Browse Server button and select the item you want. The Power Tool updates the Item ID field with the item you select. For more information about browsing an OPC server, refer to How do I browse an OPC server?
You cannot modify this setting while the item is enabled.
Transmits
Displays the number of messages sent to the OPC server from the selected item.
Receives
Displays the total number of messages the item received from the OPC server, including both synchronous and asynchronous callbacks.
Errors
Displays the total number of errors that were sent from the OPC server and received by the selected item.
Errors occur when:
- You specify an invalid item ID or access path.
- You select a requested data type that the server cannot handle.
- The OPC quality is bad.
- A read or write call fails.
For more information about the cause of the error, examine the Last Error field for the item.
Number of Items
Displays the total number of items configured for the selected group.
Access Rights
Displays the rights of the selected item in the OPC server.
Valid Entries:
- Read only: Allows you to read only from the item.
- Write only: Allows you to write only to the item.
- Read/Write: Allows you to read and write data to the item.
- Unknown: Indicates the item’s attributes are unknown at the current time. The driver is not connected to the server, the item is not active, the item ID is invalid, or the OPC server returned an invalid parameter.
Data Quality
Displays the quality of the data in the selected item. When the item is a data array, the quality applies to all values in the array. Consequently, if even one value of the array is bad, the quality of the entire array is bad.
Server Datatype
Displays the format of the data that the OPC server returns to the driver. This format does not need to be the same as the requested data type. For example, if the requested data type is Unsigned, the server may obtain an unsigned value, but return it to the driver in the form of a Float.
Read Data
Displays the last known data value read from the selected item.
Write Data
Displays the last good write value sent to the selected item.
Last Error
Displays the last error received by the item from the OPC server. For a list of errors, refer to Error Codes.
Last Read Time
Displays the last date and time that the OPC server successfully read data from the selected item.
Last Write Time
Displays the last date and time that the driver successfully wrote data to the selected item.
Last Error Time
Displays the last date and time that an error occurred for the selected item.
Block Writes Queue Count
Displays the number of items that are waiting to be written to a data array. Block writes send data to various registers in the OPC server simultaneously by using a special "send" command. This command instructs the OPC Client to send all outstanding writes in a single protocol message. Block writes are useful in batch situations where multiple setup parameters are required by the hardware at one time.
When the OPC Client sends a data array, it also sends any unmodified values in the array using the last known value.
To send block writes through iFIX, you must enable block writes in the item you want to use and then create a Digital Output block with the following address:
!Send:DataBlockName
Note that only item names are valid with the !Send control address. Server and group names do not cause any block writes to be sent to the OPC server. Analog Output blocks are not supported.
Data Monitor Button
Displays the Data Monitor for the selected item. The Data Monitor displays the data received for the item, the data's quality, and the last time data was read and written. The Data Monitor also displays the time the last error occurred for the item.
Troubleshooting
When clicked, this button displays the Troubleshooting help page.
Item Dialog Refresh Status
Displays the primary refresh rate and the refresh status for the selected item.
