ATC Mini Chiller - ModBUS Communication Protocol
ATC MINI Chiller Modbus Protocol v1 - 03 May 2019
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1 Physical Connection
The ATC MINI Chiller is provided with an RS485 serial communication interface, insulated to 1kV so that any
problem arising from ground potential is removed. While idle, the MINI Chiller is in a receive condition and only
undertakes transmission after a message has been decoded that matches the configured address. If the
checksum and data format is correct, an OK is transmitted (code 0) but if an error occurred, an error code (1+) is
sent back to the master.
The MINI Chiller is equipped with terminals named Tx+, Tx-, Rx+, Rx- and 0V to support 4 wire (full duplex) or 2
wire (half duplex) networks. The connection between slaves is wired in parallel according to the diagrams below.
A termination resistor of 120R is required at either end of the RS485 network wired pairs to prevent signal
reflection problems. A common earth or 0V line is preferred to ensure stability and transient suppression within
the system. The line can be up to 1000 meters in length and support up to 31 slaves without a repeater buffer.
Annex L-11M 190503 SA00011M RS485 ModBUS RTU for Mini
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