11
W&T
RS232(/RS422/RS485) Multi Computer Adapter
Subject to error and alteration
The DIL switch settings can be found in the following table:
Operating mode
SW1
SW2
SW3
SW4
SW5
SW6
SW7
SW8
RS232
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
RS422, RS485, 4-wire bus master
DTR handshake
OFF
OFF
OFF
ON
OFF
*
*
OFF
RS422, RS485, 4-wire bus master
RTS handshake
OFF
OFF
OFF
OFF
ON
*
*
OFF
RS485, 4-wire / 2-wire with echo
DTR control
OFF
OFF
ON
ON
OFF
*
*
OFF
RS485, 2-wire without echo
DTR control
ON
OFF
ON
ON
OFF
*
*
OFF
RS485, 4-wire / 2-wire with echo
RTS control
OFF
OFF
ON
OFF
ON
*
*
OFF
RS485, 2-Draht without echo
RTS control
ON
OFF
ON
OFF
ON
*
*
OFF
RS485, 4-wire / 2-wire with echo
automatic control
OFF
ON
OFF
ON
OFF
*
*
OFF
RS485, 2-wire without echo
automatic control
ON
ON
OFF
ON
OFF
*
*
OFF
*) Terminating the bus system when required.
The terminating DIL switches SW6 and SW7 must never be in
the ON position when using the module in RS232 mode. This
will result in a significant increase in the current draw and may
cause the RS232 driver to fail.
Termination
All RS485 modes require termination of the bus system with a
termination network. The resistor combination integrated in the
module performs two tasks in RS485 applications:
1. The connected line is terminated corresponding to its
impedance, which prevents signal reflections at the cable end.
2. In the high-impedance phases of bus operation a defined
quiescent state is ensured.
The bus system is allowed to be terminated with the terminati-
on network only in RS485 and RS422 modes, but not in RS232
mode.
Closing DIL switches 6 and 7 on the Interface Module
c o n n e c t s t h e b u s t e r m i n a l s t o t h e r e s i s t a n c e
network.
