B&B Electronics MODSCAN32 - Manual - Manual (Page 68)

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MNetMon Commands
Connect
To begin collecting data from the modbus network, you must issue the Connect menu option. MNetMon
will guide you through a series of dialogs prompting for the port assignment of the connection to the
modbus master and slave transmitters as well as the hardware characteristics of the link, (baud rate, parity,
etc). After enabling the specified serial ports. MNetMon will begin monitoring character data on the two
links. As data is received, it will be displayed to the MNetMon display as HEX characters. Data obtained
from the Master port will be displayed in Blue. Slave data will be Black.
The Disconnect menu item stops MNetMon from observing the link.
Stale Data Timer
As MNetMon recognizes slave responses to a master request for data, it will copy the data to local memory
to be used in servicing possible network clients. As data is received, it is time-stamped. Since MNetMon
only captures data as it is requested by the master, it has no way of keeping data current. It cannot poll the
slave device to refresh its data, so if for any reason, the master quits polling a particular data address, the
memory image within MNetMon will become dated. To prevent a network client from reading old data
within MNetMon, the application maintains a Stale Data Timer. Specified via the Setup Data Timer menu
option, this timer determines how long a particular piece of data is held by MNetMon before it is discarded.
If the data values are not refreshed by the time the Stale Data Timer expires, it will be removed from
MNetMon’s data base and client applications attempting to access the addresses will receive an exception
status indication from the server.
Message Statistics
MNetMon maintains timing statistics for modbus messages captured via its serial ports. A review of these
statistics may be made by selecting the View Statistics menu option.
Counters are maintained for each message received from the Master and Slave ports, as well as any message
received containing an invalid checksum. MNetMon also measures the slave’s response time to modbus
queries, and this information is displayed to the right of the statistics dialog. Shown in milliseconds, values
represent the maximum, minimum, and average response times.
Freeze Display
During an active monitoring session, the MNetMon display scrolls data as fast as it’s collected. If you wish
to stop the display from updating so you can read the character data, you may select the Freeze menu
option. When frozen, the display may be manually scrolled to observe actual message contents for
troubleshooting purposes. MNetMon continues to monitor the link and update its local data point directory
during this time. Pressing the Freeze menu selection again will return the display to its live scrolling
operation.