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bus).
10.1 Architecture
10.2 Modbus protocol
Data exchanged between the master and the D302 slave modules is defined by the MODBUS
protocol. See the attached table of Modbus transactions and addresses of variables.
10.3 Configuring the module's Modbus address
The address of the D30Xy modules is not pre-defined in the factory. They therefore do not reply
to any Modbus request. Before you can interact with a module using Modbus it must be config-
ured with a unique bus address.
10.3.1 Address configuration via the USB port
See the SLA, remote command which is used to allocate an address to the module immediately
before its
connection to the data bus. Sending a zero SLA 0 address causes the module to be deconfigured.
10.3.2 Address configuration by probe movement
This procedure enables one or more modules to be configured directly by the data bus:
•
The master starts the procedure with a broadcast bit writing process to the address 9536
(SET bit) then listens for a maximum of 60 seconds. All already configured modules are set
to sleep mode.
•
The unconfigured module for which one of the probes is moved at least 1 mm returns a zero
ASCII character to the master (outside the Modbus protocol). All other modules are set to
sleep mode.
•
The master then sends a unique module address (between 1 and 247) by broadcast word
writing to the address 8705. Only the module which is not set to sleep mode records this
address.
•
The master stops the configuration procedure with a broadcast bit writing procedure to the
address 9536 (CLEAR bit).
The procedure may be repeated if other modules without an address are still on the data bus.
11. Module power supply
The Sylvac 904.4000 charger is used to supply power to up to 4 modules connected by the bus.
If +24VDC is available on the power supply connector, 8 modules can be connected to the bus. In
all cases check that the Power LED is green on all the modules.
11
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