69
W&T
Subject to error and alteration
USB Interfaces
Modes
The RS422/RS485 port of the Interface uses DIL switches to set
one of five operating modes, which are described in brief
below:
RS422, RS485 4-wire bus master
One data and one handshake channel in each direction. The
RS422/RS485 drivers and receivers are always active in this
mode.
RS485 4-wire/ 2-wire with echo, handshake control
One data channel in each direction. The RS485 driver chip is
switched on when DTR = „ON“, whereas DTR = „OFF“ places the
driver in high-impedance state. The receive channel is always
active in this mode.
RS485 2-wire without echo, handshake control
One data channel in each direction. The RS485 driver chip is
switched on when DTR = „ON“, whereas DTR = „OFF“ places the
driver in high-impedance state. The receive channel is deacti-
vated when the driver is turned on, and activated when the
driver is in the high-impedance state.
RS485 4-wire/ 2-wire with echo, automatic control
One data channel in each direction. The RS485 driver chip is
automatically activated whenever data is sent out and placed in
the high-impedance state when data transmission is comple-
ted. The receive channel is always active in this mode.
RS485 2-wire without echo, automatic control
One data channel in each direction. The RS485 driver chip is
automatically activated whenever data is sent out and placed in
the high-impedance state when data transmission is comple-
ted. The receive channel is deactivated with the driver is turned
on, and activated when the driver is in the high-impedance
state.
