Meilhaus Electronic ME-90 Series, Electronic Manual, Page: 56 / 120

3.7.2.1.3 ME-90 PC/104-Plus
Flow control can be changed from RTS (default) to DTR signal by
jumper (see picture 31 on page 45). Controlling the receiver (echo
ON/OFF) can be adapted by a soldering bridge to the requirements
or your application if necessary (see picture 32 on page 45).
Factory setting: echo ON. The termination resistors RT have 120
Ω
and are not jumpered by default.
3.7.2.2 RS-485 half-duplex
In „RS-485 half-duplex“ operation mode, data can be either sent or
received over one twisted-pair wire. This feature is provided by the
ability of the line drivers to be set in high-impedance state besides
low and high. Note that only one transmitter can be active at any
given time. Up to 32 transmitters are allowed and the cable length
should not exceed 1200
m. Usage of termination resistors
R
T
(50…500
Ω
, depending on characteristic resistance) is
recommended.
Note:
Under Windows the configuration is done per port in the system
settings (see chapter 2.3 "Port Configuration"). Flow control is
handled automatically by the driver.
Under Linux the transmitter must be controlled by the user with
the RTS resp. DTR signal as wanted (logical „0“ sets the
transmitter driving).