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11.6 GSM call-up connection
The call-up function in the Dedicated Controls wastewater system
is used for SCADA system communication via the GSM network.
Connection is established when the SCADA system dials the CIM
250. The CIM 250 will automatically "pick up the phone" and wait
for data traffic in the form of Modbus RTU telegrams.
If legal data traffic has not been initiated within one minute, the
CIM 250 will hang up the line. This silence timeout is active
during the whole communication session. Whenever the SCADA
system has completed the Modbus communication, it hangs up
the line. This is detected by the CIM 250, which also hangs up the
line, and the call-up communication session is thereby
completed. See fig.
Fig. 18
Illustration of a GSM call-up session
If SCADA PIN code protection is enabled, the ScadaPinCode
(register 00109) has to be written with the correct value before
write access will be opened. It will then remain open until the call-
up session is completed. The next call-up session also has to
write the ScadaPinCode to be able to write registers. See
installation and operating instructions for Dedicated Controls.
Relevant settings in the CU 36X:
To find the parameter in the CU 36X, go to Settings >
Communication settings > SCADA settings >
• SCADA PIN code enabled
• SCADA PIN code.
11.7 GSM call-back connection
If an alarm appears in the Dedicated Controls wastewater system
and the SCADA call-back function in the CU 36X has been
enabled in general and also enabled for this particular alarm, the
CIM 250 will attempt to establish a phone connection to the
SCADA system. Dialling timeout is one minute, and if connection
is not established, the CIM 250 will hang up and enter a call-back
wait state. Call-back will be retried after one minute. This goes on
forever as long as the alarm condition persists. See fig.
.
If connection is established, the CIM 250 will wait up to one
minute for data traffic. If no communication is initiated from the
SCADA system, the CIM 250 will hang up, enter a call-back wait
state and retry after one minute. See fig.
The SCADA system is expected to start Modbus communication
when called. When the appropriate data have been requested or
written, the SCADA system must send a call-back
acknowledgement to the CIM 250 to signal that it has received
the information needed (Modbus writes to
PitControl.CallBackAck, register 00101, bit 5). This is to prevent
several call-backs based on the same event.
If SCADA PIN code protection is enabled, the ScadaPinCode
(register 00109) has to be written with the correct value before
write access will be opened. It will then remain open until the call-
back session is completed.
To finally end the sequence, the SCADA system hangs up the
line. This is detected by the CIM 250, which also hangs up the
line, and the call-back communication session is thereby
completed.
Fig. 19
Principle illustration of a call-back session
To find the parameter in the CU 36X, go to Settings >
Communication settings > SCADA settings >
• SCADA call-back enabled
• SCADA call-back phone number
• SCADA PIN code enabled
• SCADA PIN code.
Settings > Alarm settings >
• SCADA call-back enabled for particular alarms.
T
M
04
49
05
22
09
Dialling
Connection established
Hang-up
Modbus communication
Silence timeout after 1 min
without communication
GSM network
(e.g. SCADA)
CIM 250
Hangs up
the line.
Hangs up
the line.
Session
completed.
T
M
04
49
06
22
09
Connection established
Silence timeout after 1 min
without communication
Modbus
CallBackAck
Hang up
Modbus reply
Modbus communication
Dialling Call-back No.
GSM network, e.g.
SCADA
CIM 250
Hangs up
the line.
Hangs up
the line.
Session
completed.
Dialling
timeout
after 1
minute
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