User's Manual

Personnel Alert: Base Station
User Manual
MODBUS Wiring and Configuration
The MODBUS protocol is designed for master-slave
communication. The base station operates as a MODBUS
slave device and must be connected to a MODBUS master,
such as a MODBUS compatible PLC Control System or an
industrial PC.
MODBUS Wiring
The base station can be configured for either a 2-wire
(half duplex) or 4-wire (full duplex) MODBUS interface.
MODBUS signalling can be used to
set and clear alarm status,
read tables containing badge IDs,
read alarm acknowledgements of all badges that are
within range of the base station.
All MODBUS wiring is connected to the 2-screw down
terminal blocks, TB1 (upper) and TB2 (lower) that are
located on the main board.
Note
For 2-wire operation on the main board, the jumper
pin JP1 must be shorted (closed) by using the
supplied jumper.
Figure 12. MODBUS Wiring on Main Board
2-Wire MODBUS (half-duplex)
1. Connect the RS-485 positive lead to the +T/Rx on
TB2.
2. Connect the RS-485 negative lead to the –T/Rx on
TB2.
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