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Accessing memory using rlmodbus daemon 
  | Posted by Diego  on 24 May, 2012 - 10:38 am |
How do I access all memory of the Schneider-Electric PLC Premium? I can only read up to the %MW1024 memory location using the rlmodbus daemon (rllib library).
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> How do I access all memory of the Schneider-Electric PLC Premium?
You will have to look into the documentation of the Schneider-Electric PLC. There you should find a table with the Modbus mapping of your PLC.
rllib will simply request data from the PLC under an address you specify. Since Modbus uses 16 Bit addresses the address range is from 0 to 65536.
If the slave device (here your PLC) has data in the specified location it will respond with the according data.
But if you use an address that is not listed in the Modbus mapping of the hardware vendor the slave device will respond with an error telegram meaning that there is no data available on that address.
There may be several address ranges within one device. Normally 1 for coils and one for registers.
You will have to look into the documentation of the Schneider-Electric PLC. There you should find a table with the Modbus mapping of your PLC.
rllib will simply request data from the PLC under an address you specify. Since Modbus uses 16 Bit addresses the address range is from 0 to 65536.
If the slave device (here your PLC) has data in the specified location it will respond with the according data.
But if you use an address that is not listed in the Modbus mapping of the hardware vendor the slave device will respond with an error telegram meaning that there is no data available on that address.
There may be several address ranges within one device. Normally 1 for coils and one for registers.
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