An internal reference allows you to refer to any input, output, or parameter available in the current module. Internal references are best configured using the parameter browser available in all DeltaV expression dialogs. The browser opens a graphical list of valid blocks and parameters. By constructing a parameter path from the browser, you can avoid the potential of typographical errors and case sensitivity when referencing block parameters.
A write to an internal reference parameter changes the value of the parameter being referenced. The value of the internal reference parameter itself changes at the beginning of the next scan of the module.
The fields for an internal reference parameter are described in the following table.
|
Name and Purpose |
Type |
Configurable |
Readable |
Writeable |
|---|---|---|---|---|
|
.CST (Connection Status) - Use to see if the reference has been resolved (that is, the value has been found and can be read) |
Integer |
No |
Yes -3 means 'external reference not resolved' -2 means 'parameter not configured' -1 means 'module not configured' 0 means 'good' 1 means 'not communicating' |
No |
|
.AWST (Asynchronous Write Status) - Indicates if the last attempt to write the referenced parameter was successful |
Integer |
No |
Yes -4 means 'write rejected' -3 means 'external reference not resolved' -2 means 'parameter not configured' -1 means 'module not configured' 0 means 'success' 1 means 'not communicating' 2 means 'write pending' |
No |
|
.ST - The status of the referenced value. |
Integer |
No |
Yes |
No |
When using a reference field other than the .CV field, you will need to type the field name.