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cPCI-MXS64GX Technical Reference Manual
2.9.3.2. RS-232 Protocol:
When configured for RS-232 operation mode, the Serial Port 3 is 100% compatible with the
IBM-AT serial port signals.
2.9.3.3. RS-422 Protocol:
The RS-422 protocol (Full Duplex) uses both RX and TX lines during a communication
session.
CAUTION
In RS-422 mode,
120 ohms termination resistors (See Section 3.1 Jumper Settings)
2.9.3.4. RS-485 Protocol:
The RS-485 protocol (Half Duplex) also uses differential signals during a communication
session. It differs from the RS-422 mode as it offers the ability to transmit and receive over
the same pair of wires, and allows the sharing of the communication line by multiple stations.
This configuration (also known as Party Line) allows only one system to take control of the
communication line at the time.
In RS-485 mode, the RX lines are used as the transceiver lines, and the RTS signal is used
to control the direction of the RS-485 buffer.
When set for RS-485 mode in the BIOS, upon power-up or reset, the transceiver is by
default in receiver mode to prevent unwanted perturbation on the line. Party line operation
mode requires termination resistors to be installed at both ends of the network.
jumper caps must be installed to connect the
W8 and W9
2.12
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