Read/Write behavior of Application Server attributes
- Last UpdatedJul 17, 2024
- 2 minute read
When the system writes to an Automation object attribute, its write status is initially set to "?Pending".
When the write is completed, the #WriteSts string is updated with the result of the write. If the write completes successfully, #WriteSts value is set to an empty string. If the write returns an error and is pending, the #WriteSts item continues to show the most recent write status even if subscription updates continue to occur on reads.
You can also use the #VString1 to #VString4 items to convert float values or double values to a string format, The number N indicates the number of decimal places to be returned. For example, "3.1234" is the string for #VString4. You can use the #VString item without a number to round the float or double value to an integer and to return it as a string value.
|
Attribute Extension |
Data Type |
Purpose |
|---|---|---|
|
.#EnumOrdinal |
Integer (read/write) |
Contains the currently read ordinal value for attributes of the Qualified Enum type. This is a way to return an integer for enumerations rather than returning a string. |
|
.#ReadSts |
String (Read-only) |
Contains the current read status of the subscribed to item to which the string is concatenated. It appears as "TIC101.PV.#ReadSts". This is provided by Message Exchange as a string. Its’ value can be one of the following: "?Config"- configuration error "?Comms" - communication error "?Oper" - operational error "?Pending" - pending "?Warning" - warning "?Security" - security error "?Software" - software error "?Other" - other error Note: If the associated item (for example, TIC101.PV) is not subscribed to, the returned string is blank. |
|
.#WriteSts |
String (Read-Only) |
Contains the last write status of the item to which this string is concatenated, for example Pump1.Cmd.#WriteSts. This is provided by Message Exchange as a string. If the string is blank, the last write to the item is successful. Otherwise, #WriteSts can be one of the following values: "?Config"- configuration error "?Comms" - communication error "?Oper" - operational error "?Pending" - pending "?Warning" - warning "?Security" - security error "?Software" - software error "?Other" - other error Note: If the associated item (for example, TIC101.PV) is not subscribed to, the returned string is blank. |