Communication With A Central Controller/Dcs; Vpn Access; Setting Up Communications; Watchdog Timer - Emerson Vilter PLC Operation Manual

Blower package
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Section 12 • Communications with a Central Controller/DCS
Communication with a Central
Controller/DCS
It is possible for a central controller/DCS to read live data
and other information from the blower PLC as well as
send commands to the blower PLC. The following sec-
tion outlines the PLC addresses that are used for inter-
face between the blower PLC and central controller/DCS.

VPN ACCESS

VPN access allows Vilter engineers and technicians con-
nect remotely to the blower PLC for greater ease of sup-
port and troubleshooting. If possible, it is recommend-
ed that VPN access be provided.
To allow VPN access to a blower PLC, the following are
required:
• A physical Ethernet Connection from the blower PLC
to the site control network
• IP address, Subnet Mask, and Gateway address must
be defi ned for each blower PLC and HMI on the site
control network
• A VPN server linked to the site control network
• VPN server login information

SETTING UP COMMUNICATIONS

The blower PLC communicates using the Ethernet IP pro-
tocol. Communication to other devices compatible with
Ehternet IP is as simple as setting up CIP message in-
structions and does not require any additional hardware
other than that required for the physical connection.
Interface Data in the blower PLC is organized into arrays
for simple access of data. For example, all live instru-
ment data is arranged into a single block 200 elements
long. To get all of the data, only one message would
need to be confi gured to read an array of registers, Data
type REAL, Length of 200. See the communication ta-
bles below for specifi cs.
Setting up communications using a protocol other
than Ethernet IP is possible (Example Modbus RTU
or Modbus TCP), but additional hardware, software,
programming, and setup are required.

WATCHDOG TIMER

A watchdog timer is used to monitor the status of the
communication link between the blower PLC and Central
Controller/DCS. It is only necessary to write watch-
dog logic when the Central Controller/DCS is sending
Blower Package PLC Operation Manual •Vilter/Emerson • 35391BLP
NOTE
commands to the blower PLC. If reading data only, the
Watchdog timer is not used.
The watchdog timer works by "passing a bit" back and
forth between the Blower PLC and central controller/
DCS. If the blower PLC sees the bit in the same state
for a settable watchdog time, the communications are
faulted. The Communication fault action is selectable
between "Alarm and Revert to Local Mode" or "Trip
Machine." If "Alarm and Revert to Local Mode" is se-
lected, the blower will continue to run if running. If "Trip
Machine" is selected, the blower will trip and shut down.
The settable watchdog time and communications fault
action are selected on the Confi guration Screen.
The watchdog bits that are used are:
• Blower to Central/DCS: BOOL_OUT[0].0
• Central/DCS to Blower: BOOL_IN[0].0
When the Blower PLC sees BOOL_IN[0].0 OFF it will
turn BOOL_OUT[0].0 ON. To maintain the handshake,
the Central Controller/DCS shall Turn BOOL_IN[0].0 ON
When it sees BOOL_OUT[0].0 ON.
Data that can be Read from the
Blower PLC

LIVE INSTRUMENT DATA

Tags "REAL_OUT[0]" through "REAL_OUT[99]" present
the live data values as they appear on the HMI screen
in the selected engineering units. The Tags "REAL_
OUT[100]" through "REAL_OUT[199]" present all live
data values in base units, which are PSIA for pressures
and Degrees Fahrenheit for Temperatures. For data other
than Pressures and Temperatures, the engineering units
are fi xed and not selectable, and will appear the same in
"REAL_OUT[0]" through "REAL_OUT[99]" as they will in
"REAL_OUT[100]" through "REAL_OUT[199]." The en-
gineering units selected are presented in the tags "INT_
OUT[0]" through "INT_OUT[99]."
12 – 1

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