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The PMCS DDE Server supports both decimal and hexadecimal address formats.
Select the type of addressing you wish to use (refer to the device user manual if you
are unsure) by clicking either the Decimal or Hexadecimal radio button. Next, enter
the Start Address and End Address for the register group in the appropriate boxes.
The PMCS DDE Server supports Modbus RTU extended addressing; in decimal
mode, the range is 0 to 65535; in hexadecimal mode, the address range is 0 to FFFF.
Refer to Appendix A – Register Addressing Conventions for more information on
formatting register addresses.
Next, set the desired polling speed by clicking one of the radio buttons - Fast Poll,
Slow Poll, or Poll Once.
The polling speed is based on the scan interval for the topic. A polling speed of Fast
attempts to scan at the assigned Scan Interval. This is the default. Setting the polling
speed to Slow causes this register group to be read once every ten scan intervals. This
is typically used for setpoints or low-priority parameters that change infrequently.
Slow Poll is a multiple of Fast Poll, with a default value of 10. This multiple is
controlled by a setting in the PMCS DDE Server's .ini file, and may be changed if
desired. See the section titled PMCS DDE Server .ini File, later in this chapter.
For example, if the scan interval is set to 1000 msec (1 second – this is the default
value), setting the Poll Speed to Fast Poll causes the Server to scan as close to every
1000 msec as possible (based on the network load, communication bandwidth
availability, etc.); setting the Poll Speed to Slow Poll reduces the scan attempts to
once every 10,000 msec (10 seconds), or as close to this as possible; i.e.; not less
than 10 seconds (≥ 10,000 msec.)
Poll Once means that this register group is scanned only the first time data is
requested by a client application. All future requests for the same data receive the
data from this poll. If the device is later declared to be dead, the device is scanned
periodically until it comes back on-line, at which point the Poll Once data will be re-
Chapter Six - Advanced Options • • • • 71
DDE Server User's Guide
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