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ROC827 Instruction Manual
Issued Mar-06 Communications 5-10
The EIA-232 (RS-232) communications includes LED indicators that
display the status of the Receive (RX), Transmit (TX), Data Terminal
Ready (DTR), and Ready To Send (RTS) control lines.
Table 5-7 defines the built-in EIA-232 (RS-232) terminals at the Comm2
port and their function signals.
Table 5-7. Built-in EIA-232 (RS-232) Signal Routing – Comm2
Signal LED Function Terminal
RX Lit when Comm2 is currently receiving. 1
TX Lit when Comm2 is currently transmitting. 2
RTS Lit when Comm2 ready to send is not active. 3
DTR Lit when Comm2 data terminal ready is active. 4
GND Common. 5
The EIA-232 (RS-232) communications module provides for EIA-232
(RS-232C) signals on the Comm3, Comm4, or Comm5 port depending on
where the module is installed. Refer to Table 5-8.
Table 5-8. EIA-232 (RS-232) Communication Module Signal Routing – Comm3, Comm4, and Comm5
Signal LED Function Terminal
RX
Lit when module (Comm3, Comm4, or Comm5) is
currently receiving.
1
TX
Lit when module (Comm3, Comm4, or Comm5) is
currently transmitting.
2
RTS
Lit when module (Comm3, Comm4, or Comm5) is
ready to send is not active.
3
DTR
Lit when module (Comm3, Comm4, or Comm5)
data terminal ready is active.
4
GND Common. 5
5.8 EIA-422/485 (RS-422/485) Serial Communications Module
EIA-422/485 (RS-422/485) communication modules meet all EIA-
422/485 (RS-422/485) specifications for differential, asynchronous serial
communication transmissions of data over distances of up to 1220 meters
(4000 feet). EIA-485 (RS-485) communications are commonly used to
multi-drop units on a serial network over long distances using inexpensive
twisted-pair wiring.
EIA-422 (RS-422) drivers are designed for party-line applications where
one driver is connected to, and transmits on, a bus with up to ten receivers.
EIA-422 (RS-422) allows long distance point-to-point communications
and the drivers are designed for true multi-point applications with up to 32
drivers and 32 receivers on a single bus.
The default values for the EIA-422/485 (RS-422/485) communications are
19200 Baud Rate, 8 Data Bits, 1 Stop Bit, and No Parity. The maximum
rate is 57.6K bps.