User's Manual

FEATURES AND OPERATION
2-7
Part No. 001-4090-101/102
2.4.1 OPERATING MODES
Integra-H has two operating modes for its COM port: (selectable via the RSS program)
DOX mode: The RS-232 port is monitored for incoming data. Upon receipt of the first data
byte, the transmitter is turned on. The RTS signal is ignored (Note: RTS may still be used as a wakeup
signal for a unit that is asleep).
RTS mode: The RTS signal is monitored for a low-to-high transition. This transition causes
Integra-H to turn on its transmitter. CTS is raised 4 ms later to accommodate DTE that requires a CTS
transition before it can send data. The transmission will continue until RTS is dropped or until the Tx
Time out (see section 2.8) expires.
CTS is used as a handshaking/flow control signal in both modes. If the Integra-H’s buffers fill,
CTS will be dropped as a signal to the DTE to stop sending data. This condition is most likely when the
Data port speed exceeds the radio network speed. In such cases, reduce the DTE baud rate so that
Integra-H buffers will not fill.
2.4.2 DATA FORWARDING TIMER
The data forwarding timer can modify the timing between data blocks in a transmission to
accommodate some RTU's special timing requirements. Set to “normal” (15 ms) unless advised
otherwise by technical support. Do not use “fast” (5 ms) timer below 2400 baud.
2.4.3 SENDING BREAK SIGNALS
Integra-H may be configured to send “break” signals, as required by some SCADA user
protocols. A break signal is generated by holding TXD in the zero state for longer than one character
time. Indication of a break signal is carried in a special data transmission to the remote station, which in
turn generates its own output break signal.
At a port speed of 19200 b/s, the output break signal has a duration of 5 to 10 ms, regardless of
the duration of the input break signal. These times are scaled proportionally for other baud rates. Integra-
H may also be set to ignore “break” signals in order to prevent spurious transmissions when terminal
equipment is powered on and off.
2.4.4 COM PORT BAUD RATES
The COM port operates at standard baud rates from 300 to 19200 b/s. Baud rate is set using the
Integra RSS and is independent of the network speed setting.
We recommend that the COM port baud rate be set to a speed less than the network speed.
Setting a COM port baud rate higher than the network rate may result in data buffers filling, which in
turn may cause Integra-H to drop CTS. This could have detrimental effects on some protocols,
particularly those that ignore CTS.