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ASYNC 232
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422/485 CONVERTER
S1-4: Echo Mode
The setting for switch S1-4 determines whether the Converter echoes data
back to the transmitting device (half-duplex mode only).
S1-4
Setting
On
Echo On
Off
Echo Off
S1-5: Carrier-Control Method
The setting for switch S1-5 determines whether the carrier is “Constantly
On” or “Controlled by RTS.” This setting allows for operation in switched-
carrier, multipoint, or hardware-handshaking applications.
S1-5
Setting
On
Controlled by RTS
Off
Constantly On
NOTE
Carrier is ON when RTS is asserted positive, and OFF only when RTS is
driven to a negative voltage.
S1-6: Receive Impedance (Termination)
The setting for switch S1-6 selects the impedance of the input receiver. You
may select either a “low” impedance of 120 ohms or a “high” impedance of
16K ohms. By selecting the proper impedance for each drop, there may be
up to 31 receivers in one application.
S1-6
Setting
On
Low (120 ohms)
Off
High (16K ohms typical)
S1-7 and S1-8: 2-wire/4-wire Modes
Switches S1-7 and S1-8 are set together to determine whether the
Converter is in 2-wire or 4-wire operating mode. Note: 2-wire mode is half-
duplex only.
S1-7
S1-8
Setting
On
On
2-wire mode
Off
Off
4-wire mode
