Instruction manual

ControlWave Gas Flow Computer (GFC Plus) Instruction Manual (CI-ControlWave GFC Plus)
2-30 Installation Revised Feb-2013
Figure 2-19. Connection from a case-mounted Modem/Radio to COM2
of the ControlWave GFC Plus
When interfacing to the COM3 port of a ControlWave, or the COM5 or
COM6 port a ControlWaveEXP unit, use the cable presented in Figure
2-20 along with one of the cables shown in Figure 2-17 or Figure 2-18.
Figure 2-20. Full-duplex and Half-duplex Cable
RS-232 Cable
Guidelines
Observe the following guidelines when constructing RS-232
communication cables:
 Ensure that DCD is high to transmit (except when dialing a modem)
 Verify that each RS-232 transceiver has one active receiver while
disabled (in power down mode); connect the DCD signal to the
active receiver.
 Set CTS to high to transmit.
 If the port is set for full-duplex operation, RTS is always ON.
 Ensure that DTR is always high when port is active; DTR enables
RS-232 transceivers.
Note: Control DTR using the PORTCONTROL function block and
the _Pn_AUTO_DTR system variable in your ControlWave
project. If you turn DTR off through these mechanisms, the
port remains off, even though hardware is fully configured.
 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 surge protectors.