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48 • • • • Chapter Four - Menus and Toolbars
The PMCS DDE Server doesn't just look at individual devices directly; instead it
uses a more flexible virtual addressing scheme, which looks at topics at particular
addresses. A topic consists of a user-specified device name, port number, address,
and device type, and information on how often it is to be scanned. While there is
usually just a single topic per device, it is possible to have multiple topics obtaining
data from the same device. Why would you want to do this? This feature offers the
ability to scan different data from the same device at different intervals.
For example, suppose you want to scan a set of registers at one device every 1000
milliseconds, while for other registers a 5000 millisecond scan is adequate. In this
case, you could set up two separate topics, each addressed to the same device, but set
to scan at different scan intervals.
Enter a name for the device. This will be the topic name referenced from client
applications. This name must be unique, must begin with an alphabetic character, be
no more than 20 characters long (8 characters if used with a third-party HMI client).
Only alphanumeric characters and underscores are permitted; the topic name cannot
include spaces or special characters, such as: + * / /, ? () " '.
Click on the down arrow key to select the communication port. Only configured ports
are listed in the comm port list box; a device cannot be assigned to an unconfigured
port.
NOTE: If no comm ports have been configured, the Device Configuration dialog
box is not displayed. You must select Cancel, configure one or more comm ports
according to the procedures described earlier, then return to this procedure.
Select the Device Type from this list.
Enter the Slave address assigned to the device in this field. On a single RS-485
network, all addresses must be unique, though it is acceptable to have devices with
the same address if they are on different RS-485 networks. For example, Network 1,
Device 1 is recognized as different from Network 2, Device 1.
The device addresses must fall into the following ranges:
•
POWER LEADER Modbus Concentrators must have addresses in the
range 1 – 32.
•
Commnet devices must have addresses in the range 33 – 247.
•
Modbus devices other than the Modbus Concentrator may have
addresses in the range 1 – 247.
For details on addressing requirements, refer to GEH-6502, PMCS Network
Architecture Guide.
DDE Server User's Guide
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