English (GB)
60
A common standard for call-back via GPRS does not exist. In the
CU 36X, this function is implemented as a Modbus TCP write
telegram sent from the CIM 250. See fig. 21.
Fig. 21 Modbus TCP telegram used for call-back via GPRS
The call-back telegram is a "Write single register" function that
writes the value of 0x00FF to a specific register address in the
Modbus TCP master. Which register address to write to can be
programmed in the ScadaGprsCallBackRegister (register 00007).
In fig. 22 the address is 0x0001. The Modbus TCP master must
interpret this as a call-back request from the CU 36X and start
polling for data within one minute, otherwise the Modbus TCP
write telegram will be resent.
The SCADA system must complete its communication with the
CIM 250 by issuing a call-back acknowledgement.
If call-back is to be used, the SCADA system software (Modbus
TCP driver) must support this procedure.
If more clients are "Connected" simultaneously, they will all
receive the call-back, and any of them will be able to terminate
the call-back sequence.
Fig. 22 GPRS via VPN tunnel
Fig. 23 GPRS call-back sequence
Relevant settings in the CU 36X:
To find the parameter in the CU 36X, go to Settings >
Communication settings > SCADA settings >
• SCADA call-back enabled.
Settings > Alarm settings > System alarms >
• SCADA call-back for particular alarms.
TM04 4909 2809
Transaction ID
Protocol ID
Length
Slave address
Function code
Register address
Value to write
0x**
0x**
0x00
0x00
0x00
0x06
0xE7
0x06
0x01
0x00
0xFF
0x00
Has the value of the
The selected slave
Write single registe
Value 0xFF00 writte
Has the value of the
latest transaction ID
minus 10
Selected slave address,
shown is default value
Value 0xFF00
written to register
0x0001
Write single register
TM04 4908 2209
PC Tool, etc.
SCADA system
Clients
LAN
GRE router
GRE router
VPN tunnel
Internet
GSM operator
GSM network
Base station APN
CIM 250 GSM
module installed
User
Setup/status
"Static" IP
address
TM04 4910 2209
Modbus TCP write request
Modbus TCP CallBackAck
GSM network,
e.g. SCADA
CIM 250
Internal
acknowledge
of call-back.
Ready for new
call-back.
Silence
timeout after 1
minute.
Modbus TCP
request will be
retransmitted.
GPRS data exchange
ScadaGprsCallBackRegister
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