Created: January 19, 1993
Updated: June 28, 2001
InTouch? and the Wonderware?I/O Servers provide a way to monitor the communications status in an application. The IOStatus built-in topic (DDEStatus in FactorySuite? 1000 and the earlier versions of InTouch) can monitor the status of connection between InTouch and a data server. This connection can be between InTouch and Microsoft Excel, InTouch and an I/O Server, or two InTouch nodes in a networked application. Also, the Status bit in an I/O Server that was developed with the Wonderware I/O Server Toolkit? monitors the communication status between the I/O Server and the PLC. Once both bits are configured, they can flag you for trouble or provide a trigger for an immediate switchover to a standby PLC or computer. Status Item
The Status bit is a built-in item available for each topic configured for the I/O Servers developed with the Wonderware I/O Server Toolkit. Example
1. Suppose we have two DDE Topics defined in the I/O Server and two
DDE Access Names, PLC1 and PLC2, which are defined as follows: DDE Access Name: PLC1 PLC2
Application/Server Name: Modbus Modbus
Topic: PLC1 PLC2
2. We would then create two Discrete tags, PLC1Status and PLC2Status.
o Each tag will monitor the status of the two conversations
between the I/O Server and the PLCs.
3. In WindowMaker, select Special/Tagname Dictionary and define the
two tagnames as follows:
Tagname: PLC1Status PLC2Status
Type: I/O Discrete I/O Discrete
DDE Access Name: PLC1 PLC2
Item: Status Status
o PLC1Status and PLC2Status will have a value of one when there
is an active conversation between the DDE Topic in the I/O
Server and the PLC.
o Both will go to zero when the conversation is lost.
Note: For the status bit of a topic to be valid, at least one item
other than the status bit needs to be advised in the same topic.
There is an IOStatus bit for each DDE Access Name that is defined in an InTouch application.
1. Suppose we have three DDE Access Names that are defined as follows: Access Name: Master PLC1 Sheet1
Node: Master Master
Application Name: View Modbus Excel
Topic Name: Tagname PLC1 [Book1]Sheet1
o The Access Name Master is used to talk to InTouch on a computer
with a node name of Master.
o The Access Name PLC1 is used to talk to a Modbus I/O Server
on a computer with a node name of Master.
o The Access Name Sheet1 is used to locally talk to an Excel
spreadsheet named Sheet1.xls on the same computer. Using this information, we can use the IOStatus bit to monitor the conversations set up by these Access Names by performing these steps:
2. In WindowMaker, select Special/Configure/Access Names.
3. Select New and define the IOStatus as follows:
Access Name: IOStatus
Application Name: View
Topic Name: IOStatus
4. Create three Discrete tags in which each tag monitors the status
of the three I/O conversations.
5. In WindowMaker select Special/Tagname Dictionary and define three
tagnames as follows:
Tagname: Master_Status PLC1_Status Sheet1_Status
Type: I/O Discrete I/O Discrete I/O Discrete
DDE Access Name: IOStatus IOStatus IOStatus
Item: Master PLC1 [Book1]Sheet1
o The following diagram shows the relationship between the tags
and Access names for the Modbus Access Name with the PLC1
Note: The IOStatus will have a value of one when there is an active conversation between InTouch and the respective application and Topic that are being monitored. The tags will go to zero when the conversation is lost, or when there are no active items using the Application and Topic that are being monitored. Therefore, for IOStatus to be valid, at least one tag must use the Topic being monitored at all times.
It is not recommended to use IOStatus as the only means to monitor the communications between InTouch and the I/O Server. Wonderware Tech Support strongly favors the use of a heartbeat (a timer or free-running
counter on the remote View node or PLC) to monitor the communications (see related articles below for more details). The reason for that is that IOStatus uses the TCP stack built into Windows for communications, and it may take a few seconds for the stack to time out when there is no communications (the server is closed, there is a power failure, or the cable is disconnected). Or, it is also possible that the stack does not detect the communications failure and the IOStatus will not detect the condition either.
For more information and details about the use of a heartbeat to monitor communications between InTouch and the I/O Server, please read the following articles.
; Follow this link to Setting Up a "Heartbeat" Between Two InTouch
; For an example of a hot backup strategy for PLCs using Status, see
Configuring a "Hot Backup" Strategy for I/O Servers Using the Status
; For more information on configuring InTouch backup applications,
see Configuring a "Hot Backup" Strategy for PLCs, I/O Servers, or