Specifications

85
Schneider Electric
Summary
RS232C:
b Limit length to 15 m.
b Take into account the specific requirements of each interface and software
program with regards to management of control lines (RTS/CTS) when connecting
the line.
RS232/RS485 interface:
b Use converters recommended by Schneider Electric whenever possible; they have
been tested and validated for proper operation regardless of the configuration of the
installation.
RS485 link:
b Choose a 2-wire connection over a 4-wire link whenever possible.
b Use shielded twisted pairs with a characteristic impedance of 120 W.
b Link earths carefully.
b Make sure there are load resistors (120 W) on each side of the communication
line, as well as polarisation resistors, preferably on the "Master" side.
b Limit slaves to 32.
Modules:
b Each module has its own address. Make sure communication speeds and formats
used (data, parities, stop) are the same.
Modbus protocol:
b Do not mix Modbus ASCII and Modbus RTU products.
b Verify conformity between functions implemented in the modules connected and
functions used by the supervisor.
b Respect the various time constraints in the protocol.