Essential Services Operation (Eso); Local / Remote Mode Selection; Modbus Quick Set-Up Guide; Modbus Setup And Operation - Zener MSC-3 Instruction Manual

MODBUS Setup and Operation

Setting up the MSC-3 for various applications with MODBUS communications is similar to conventional
wired control using the terminal strip. The interactions between wired control and MODBUS features are
as follows:
Local mode
Control of the run function (ie starting and stopping) is from the console. MODBUS commands do not
influence the starting and stopping of the MSC-3 in local mode. The speed reference used for local
operation is determined by the reference source selected by parameter F02 LOCAL REF. See list of
speed references for available choices.
Remote mode
Control of the run function (ie starting and stopping) is either from the terminal strip or by MODBUS
depending on the setting of G166 RUN SIGNALS. Available choices are FROM TERMINALS or
FROM NETWORK. Setting this parameter to FROM TERMINALS allows the terminal strip alone to
control the run function. Selecting FROM NETWORK allows the MODBUS network alone to control the
run function via binary value objects "Run fwd" and "Run rev"
Reset
Reset commands from all sources (terminal strip, internal MSC-3 functions and MODBUS) are honoured
at all times.
Network Speed Reference
If the speed reference for the MSC3 in any given mode is to be determined by the network system, the
reference to select is COMMS_REF.

Essential services operation (ESO)

ESO mode selection from all sources (wired terminal or MODBUS ESO coil) is honoured at all times.
CAUTION
Loss of communications is a loss of ESO if an ESO terminal not set up.

Local / remote mode selection

Control of local/remote mode is always from the terminal strip. Operation of the MSC-3 may be
monitored via MODBUS regardless of the local/ remote mode.

MODBUS Quick Set-up Guide

1. Set up all the usual menu items according to the application needs.
2. Set the various MODBUS related menu items BEFORE connecting the network. This will avoid
disrupting the MODBUS network unnecessarily.
• G160 Protocol: Ensure MODBUS RTU is selected
• G161 bits/sec: Select the baud rate to suit the MODBUS system.
• G162 Parity: Select the parity to suit the MODBUS system
• G163 MAC/Dev ID: This value must be unique for every MODBUS device on the BACnet MS/TP
network segment that the MSC-3 is connected to.
• G166 RUN SIGNALS: This parameter determines if run commands are taken from the MSC-3
terminals or from the MODBUS interface.
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