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SpecView supports the DDE Advise mechanism for supplying DDE Clients with data. (restrictions).

Read the DDE Read Example

SpecView listens on the 'var' topic  (or that setup by the user in Preferences - DDE) for an item that is the name of the variable you want to read.  The format of the item is:

 Instrument <dot> parameter <comma> rate(optional)

All items are not case sensitive, and the parameter can be either the short or long name of the parameter.

The rate can be omitted, in which case 'medium' is assumed, or can be specified as M,L,H or U, meaning Medium, Low, High, Ultra-High rate.  The actual rate used depends on

the settings for the project.

For example:

Zone1.pv                        Gets process value at medium rate

Zone1.Process Val                The same

Zone1.PV,m                        The same

zOnE1.PROCess VAL,M        Still the same.

Zone1.PV,U                        Gets the PV at the Ultra High Rate.

When a request for a new variable comes in via the DDEAdvise mechanism, it is checked by SpecView to see that the variable exists.  If it does exist, then SpecView begins to request that variable over comms and from then on supplies the Client with the data at the given rate (or faster), until the Client signals that data is no longer required.  If the variable does not exist, then the SpecView DDE Status information reflects this.

NOTE: Due to the potentially long startup time of any given request, a blank answer is sent back to the DDE Client first.  Thus, the very first item of data from SpecView should be ignored for each new item that is requested.

In the event of comms errors or missing instruments, no data is sent across DDE.

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