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LEVELtrol-II Installation & Operating Instructions
10. RS-485 Serial Port (optional)
10.1 RS-485 Port Description:
The LEVELtrol-II has a an optional general purpose RS-485 Port which may be used for any one of the
following purposes:
Accessing Process Parameters
Level, Temperatures, Pressures, Density, Time & Date, Setpoints, etc.
Accessing System Alarms
System, Process, Alarm Status
Accessing Totalizers
Mass, Corrected Volume, Volume Totalizers and Grand Totalizers
Executing Various Action Routines
Reset Alarms, Print Transaction, Reset Error History, Batch ??????
10.2 General
The optional RS-485 card utilizes Modbus RTU protocol to access a variety of process parameters and
totalizers. In addition, action routines can be executed. For further information, see Appendix C.
10.3 Operation of Serial Communication Port with PC
LEVELtrol-II’s RS-485 channel supports a number of Modbus RTU commands. Refer to port pinout
(below) for wiring details. Modbus RTU drivers are available from third party sources for a variety of
Man Machine Interface software for IBM compatible PC's.
The user reads and writes information from/to the RS-485 using the Modbus RTU commands. The
LEVELtrol II then responds to these information and command requests.
Process variables and totalizers are read in register pairs in floating point format. Time and date are
read as a series of integer register values. Alarms are individually read as coils. Action routines are
initiated by writing to coils.
10.4 LEVELtrol-II RS-485 Port Pinout
LEVELtrol-II RS-485 Port Pinout
(recommended mating connector: DB-9M)
1 Ground
2 Ground
3 Ground
4 TX/RX (+)
5 TX/RX (-)
6 Do Not Use
7 Terminating Resistor (180 Ω)
8 TX/RX (+) (spare internally connected to 4)
9 TX/RX (-) (spare internally connected to 5)
LEVELtrol-II RS-485 Port Pinout
(Terminal Block Option)
1 Common
2 TX/RX (+)
3 TX/RX (-)
4 Terminating Resistor (180Ω)
1
2
3
4
5
6
7
8
9
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
RS-232
RS-485
1 2
Phone Line for
Internal Modem
Option
1 2 3 4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
6
7
8
9
RS-232
RS-485
Phone Line for
Internal Modem
Option
1 2
