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• Incorrect RS-485 connections. The TXA lead of the local unit should be
wired to the RXA lead of the remote unit. The TXB lead of the local
unit should be wired to the RXB lead of the remote unit. The RXA lead
of the local unit should be wired to the TXA lead of the remote unit.
The RXB lead of the local unit should be wired to the TXB lead of the
remote unit. Polarity (A to A, B to B) must be observed.
• The maximum link distance has been exceeded. Check by selecting a
lower baud rate. If the units function at a lower baud rate, the distance
has been exceeded.
• Unsuitable link termination in multipoint configurations. Switch the
present terminated slave unit to the unterminated state and select
another slave unit for termination. In some configurations (especially
those having a large number of slaves with widely varying distances), the
selection of the best slave unit for link termination can be a trial-and-
error process.
CHAPTER 5: Test Modes
