Specifications

50
Schneider Electric
Interfaces
RS232/RS485
Definition of an RS232/RS485 interface:
b RS232:
v conformity with the EIA standard,
v PC connection cable < 20 m,
v transmission speed compatible with PC port,
v management of flow / presence control signals:
- RTS (Request To Send); DTE ÆDCE,
- CTS (Clear To Send); DCE ÆDTE,
- DCD (Data Carrier Detect),
- DSR (Data Set Ready)
- DTR (Data Terminal Ready) DCE Æ DTE.
v if it is possible to choose the type of interface (DTE/DCE), choose DCE.
b RS485:
v conformity with the EIA standard,
v connection cable < 1200 m,
v transmission speed compatible with equipment,
v possibility of line polarization (Rp),
v possibility of line load (Rp),
v 2 wire or 4 wire management,
v conformity of data format (start, stop, parity, etc.)
v possibility of 32 modules (at least) on its line.
All personal computers used in offices are
equipped with at least one serial port
(COM1) that is specified by standard
RS232C. An adapter (interface RS232/
RS485) for electrical levels is required. In
some cases, such as for "industrial" PCs,
an adapter is not required if a card
supporting standard RS485 can be
installed.
Guide to Integration
Modbus / Jbus