- Emerson Remote Terminal Unit Instruction Manual

2-12 / Installation & Operation CI-ControlWave Express
Diagrams of RS-232/485 interfaces and connectors are shown in Figures 2-4 and 2-5
Hardware connector pin wiring assignments are provided in Tables 2-3A through 2-3C.
2.3.3.3 RS-232 & RS-485 Interfaces
ControlWave Express RS-232 & RS-485 communication schemes are discussed herein.
2.2.3.3.1 RS-232 Ports
An RS-232 interface supports Point-to-Point, half-duplex and full-duplex communications
(20 feet maximum, using data quality cable). Half-duplex communications supported by the
ControlWave Express utilize MODBUS or BSAP protocol, while full-duplex is supported by
the Point-to-Point (PPP) protocol. ControlWave Express RS-232 ports utilize a “null
modem” cable (Figure 2-5A - Top) to interconnect with other devices such as a PC, printer, a
ControlWave series unit (except CW_10/30/35) when the ControlWave Express is
communicating using the full-duplex PPP protocol. A half-duplex cable (Figures 2-5A -
Bottom) may be utilized when the ControlWave Express is connected to a ControlWave
series unit (except CW_10/30/35). If communicating with a Bristol series 3305, 3310, 3330,
3335, or CW_10/30/35 RTU/DPC, one of the cables shown in Figure 2-5B must be used.
Refer to Figure 2-5C to connect ControlWave Express serial RS-232 port COM2 to either an
external modem or external radio. When interfacing to Port COM3 of a ControlWave unit,
or to COM5 or COM6 of a ControlWaveEXP, the cable of Figure 2-5D must be used along
with the one of Figure 2-5A or 2-5B. Tables 2-3A through 2-3C provide the connector pin
assignments for ports COM1 and COM2.
Note: The following facts regarding ControlWave Express RTU’s RS-232 serial
communication ports should be observed when constructing communications cables:
• DCD must be high to transmit (except when dialing a modem)
• Each RS-232 transceiver has one active receiver while in power down mode
(disabled); the DCD signal is connected to the active receiver.
• CTS must be high to transmit.
• When port is set for full-duplex operation - RTS is always ON.
• DTR is always high (when port is active); DTR enables RS-232 Transceivers.
• When port is set for half-duplex operation - CTS must go low after RTS goes low.
• All RS-232 Comm. ports support RTS, DTR, CTS, DCD and DSR control signals.
• All RS-232 Comm. port I/O signals are protected by LCDA12C surge protectors
to ±4KV ESD.
Table 2-3A - RS-232 Ports (COM1 & 2) Connector Pin Assignments
(D – Connector: COM1 Connector J4, COM2 Connector TB3
Pin
#
Signal
RS-232
Description:
RS-232 Signals
1 DCD Data Carrier Detect Input
2 RXD Receive Data Input
3 TXD Transmit Data Output
4 DTR Data Terminal Ready Output
5 GND Power Ground
6 DSR Data Set Ready Input
7 RTS Request To Send Output
8 CTS Clear To Send Input
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