W&T 18801, Руководство пользователя

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71
W&T
Interface modules
Subject to error and alteration
Operating modes
The Interface Modules are configurable for the following
modes using DIL switches:
RS422
The Interface Module supports one data and one handshake
channel each (selectable DTR or RTS handshake output). The
RS422 sender/receivers are always active.
RS485
One data channel in each direction is always available in all
RS485 modes. These modes differ only in how the RS485
transceivers are controlled.
RS485 4-wire bus master
In this mode the master uses a conductor pair to send
requests to the slaves, which in turn send their replies to the
master on an additional common conductor pair. The RS485
transceivers are always active in this mode, whereby the master
can always send and is constantly listening for the slaves.
RS485 4-wire mode with handshake control
The RS485 driver chip is turned on with a TTL Low level on the
„DTR“ or „RTS“ line, whereas a TTL High level on this line puts
the driver in a high-impedance state. The receiving channel in
this mode is always active.