25
Notes:
1. Each controller in a SCADA system using the Modbus protocol is assigned a unique Slave Address
so that it can be polled by the SCADA system Master using that unique Slave Address.
However, if
communication is through the optional Ethernet Port, each controller will already have a unique IP
Address. When the Slave Address Parameter P.28 is set on zero, the controller will not reject mes-
sages based on the Slave Address, and it will copy the incoming Save Address for use in the Re-
sponse.
2. The Register Access Mode Parameter (P.33) is provided to prevent (when set on Read Only) mali-
cious attempts to remotely control the pumps, or change setup parameter values. Unless greatly
needed, the Register Access Mode should be left on Read & Write.
Function
Code Function Description Notes
01 Read Coil Status
02 Read Input Status
03 Read Holding Registers
04 Read Input Registers
05 Force Single Coil
06 Preset Single Register
08 Diagnostics - Sub-function 00 (Return Query Data)
15 Force Multiple Coils Limited to 100 Coils
16 Preset Multiple Registers Limited to 35 Registers
MODBUS Functions Supported
COMMUNICATION WITH A SCADA SYSTEM
A SCADA system may communicate with the controller through either the RS232 Serial Port or through the
Optional Ethernet Port. The controller operates as a MODBUS slave, where all communication is initiated
by the MODBUS master.
Setup for Connection to a SCADA System
Parameter
D
efault
Value Setting Definitions
P.28 1 Slave Address (See note 1 below.) Range: 0 -
247
P.33 1
Register Access Mode (See note 2 below.)
1
=
Read & Write 2
=
Read Only
Current
Value
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