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Protocol Timer Tick – The time interval at which the Server executes DDE protocol;
how often the Server listens for an incoming message from a device or transmits a
message to a device.
Register – Location in a device's memory containing a single binary datum. Each
register has a particular address, and the DDE Server can access a register's data by
specifying the device and the register's address. Mnemonics are used to make the
numeric register addresses more meaningful; for example, VOLTS_A is
understandable as the volts on phase A of a particular device, whereas the actual
register address might be R10024-A1, which conveys no meaning to the reader.
Register Map – Comprehensive listing of all register addresses and what they
contain.
Scan Interval – Defines how often a device is to be scanned under optimal
conditions; this is a target time which may not be attained due to network traffic load,
number of devices, amount of data being requested, etc. A scan interval of 1000 msec
(1 second) indicates that the DDE Server will attempt to scan the device as close to
once per second as it can.
Server – A DDE-compliant MS Windows application providing data to other DDE-
compliant applications (clients) on their request.
Time-out – The error message generated when no reply is received to a query after a
given period of time.
Topic – A user-defined name associated with a specific device set to be polled at a
particular frequency.
Valid Data Time-out – The time (in milliseconds) that elapses after a client has made
a request for data to the PMCS DDE Server before a time-out error message is
returned to the client.
88 • • • • Glossary of Terms
DDE Server User's Guide
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