SMAX MODBUS®
4.3 Node address
The node address of the device is set via software in the
The default address preset by Lika is 1. The address must have a value between 1
and 247.
NOTE
The default address is 1.
The address 0 is reserved to identify a “broadcast” exchange (Master sends a
request to all Slaves connected to the Modbus network). See the “6.1 Modbus
Master / Slaves protocol principle” section on page 44.
The Modbus Master node has no specific address, only the Slave nodes must
have an address. Each Slave must have a unique address.
Addresses from 248 to 255 are reserved.
If you set the address 0, device will be set to 1 automatically.
Equally, if you set an address higher than 247, device will be set to 1
automatically.
4.4 Data transmission rate: baud rate and parity bit
The data transmission rate (baud rate and parity bit) is set via software in the
Serial com baud rate [0005 hex]
register (see on page 65). The default value
is 04 hex = Baud rate 19200 bit/s, Parity bit Even.
4.5 Bus termination resistor
WARNING
Power supply must be turned off before performing this operation!
As the RS-485 cables have an impedance of typically 120 it is necessary to
Ω
always add a termination resistor (RT) in order to minimize cable reflections and
ensure a defined noise level on the data lines. The termination resistor must be
installed at both physical ends of the line: at the beginning of the RS-485
communication bus (typically in the PLC) and at the end of the bus, in the last
slave of the line. We recommend a 120 termination resistor to be used. The
Ω
termination resistor has to be provided between the A_RS485 OUT and the
B_RS485 OUT signal wires in the last slave of the line, as shown in the Figure
below.
MAN SMAX MB E 1.2
Electrical connections
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