PureAire Monitoring Systems, Inc.
10/25/07
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3.3.2 Modbus RS-485 Serial Interface
The Modbus RS-485 Serial Interface board allows up to 128
Air Check
✓
EX
gas monitors to communicate to a Modbus master device on a single cable. The
gas detector functions as a slave device; a PLC or PC running MMI or BUI
software equipped with a Modbus driver functions as the master.
The RS-485 standard allows cable lengths up to 4000 feet between the Modbus
master and slave. Both 4-wire full duplex and 2-wire half duplex connections are
supported by the Modbus RS-485 serial interface option.
NOTE: See Appendix for RTU address, Registers, and Function Code
information.
