59
W&T
Subject to error and alteration
USB Interfaces
Operating modes
The combined RS232/RS422/485 port on the Interface can be
set to various operating modes using DIL switches inside the
unit, which are described in brief below:
RS232 mode
One data channel in each direction (RxD and TxD) is supported
as well as six handshake channels (RTS, CTS, DSR, DCD, DTR
and RI).
RS422 mode
The Interface supports one data and one handshake channel
(selectable DTR or RTS handshake output) in each direction.
The RS422 transceivers are always active in this mode.
RS485 mode
In all RS485 modes there is one data channel available in each
direction. The operating modes differ only in how the RS485
transceivers are controlled.
RS485 4-wire bus master
In this mode the Master sends requests to the Slaves over a
pair of wires, and the Slaves send their replies to the Master
over another common wire pair. The RS485 drivers and recei-
vers are always active in this mode, whereby the Master can al-
ways send and is continuously listening for the Slaves.
RS485 4-wire mode / RS485 2-wire mode with echo
There is one data channel available in each direction. The
RS485 driver chips is automatically activated each time data is
sent and then switched to tristate at the end of data transmis-
sion. The receiver channel is always active in this mode.
RS485 2-wire mode without echo
There is one data channel in each direction available. The
RS485 driver is automatically activated each time data is sent
and switched to tristate after the end of data transmission. The
receive channel is deactivated when the driver is on, and on
when the driver is in tristate.
