Hitachi ABB RVT Installation Und Betriebsanleitung Seite 633

The choice of the RS-232 / RS-485 is then particularly important as a bad management of the direction of transmis-
sion may lead to communication errors or no communication at all. If RTS is released too early, the query will not ar-
rive to the Modbus slave and no answer will be initiated. If RTS is released too late, the answer will not be received
completely by the Modbus master.
As a consequence, to ensure higher throughput and reliable communication, the recommendation is done to choose
an RS-232 / RS-485 able to sense and manage the data direction, and to avoid any computer dependent flow control.
Missing to do so may lead to force the user to work with a slower transmission speed.
An also important feature is the isolation between the RS-232 side and the RS-485 side to avoid ground loops and to
work safely.
Finally, port powered converters should be considered carefully as some computers don't have sufficient power to
feed efficiently the RS-232-RS-485 converter.
STATUS
Approved
SECURITY LEVEL
Public
DOCUMENT ID
9AKK107045A9895
RS 48 5 A DAPTE R
REV. LANG. PAGE
E en 20/21
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