NTI ENTERPRISE ENVIRONMENT MONITORING SYSTEM
98
MODBUS TCP/IP SUPPORT
The ENVIROMUX is equipped with Modbus TCP/IP support to enable PLC controls to read the value/state of sensors and read
and command the state of relays. Using the Modbus communication protocol devices can be programmed over TCP/IP to treat
the ENVIROMUX as a Modbus slave device reacting to readings from available sensors and controlling relays as needed.
Modbus TCP Function Codes Definition
Function Code Name Usage
01 Read Coils Read the state of Output Relays
02 Read Discrete Inputs Read the state of Digital Inputs
03 Read Holding Registers Not Available
04 Read Input Registers Read Internal/External Sensors floating point values
05 Write Single Coil Write data to force Output Relay Active/Inactive
06 Write Single Holding Register Not Available
15 Write Multiple Coils Write data to force multiple Output Relays Active/Inactive
16 Write Multiple Holding
Registers
Not Available
Function Code 01 - Read the state of Output Relays
Description:
Function code 01 is used to read the status of Output Relays (Active/Inactive) of the ENVIROMUX-xD slave device in a binary
data format.
Query:
Slave
Address
Function
Code
Starting
Address High
Starting
Address Low
Quantity of
coils High
Quantity of
coils Low
CRC CRC
Response:
The Relay Outputs status in response message is packed as one Relay Output per bit of data field. The first Relay Output
addressed by Starting Address is the LSB. A value of “1” for a bit means that the relay is INACTIVE while “0” means relay
ACTIVE.
Mapping:
Coil # (Address) ENVIROMUX-16D ENVIROMUX-5D ENVIROMUX-2D
0 Relay Output #1 Relay Output #1 Relay Output #1
1 Relay Output #2 Relay Output #2 N/A
2 Relay Output #3 N/A N/A
3 Relay Output #4 N/A N/A
4 Remote DO #1-1 Remote DO #1-1 Remote DO #1-1
... ... ... ...
19 Remote DO #1-16 Remote DO #1-16 Remote DO #1-16
20 Remote DO #2-1 Remote DO #2-1 Remote DO #2-1
… ... ... ...
35 Remote DO #2-16 Remote DO #2-16 Remote DO #2-16
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