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Hi,
can anyone please tell me that what the procedure of replacing the cpu of s7 300 plc with s7 400?

Hello;
S7-300 and S7-400 PLCs are very different beasts, in terms of power and physical setup. The form factor of the modules is different (the S7-400 modules being twice as high as their S7-300 equivalents)and the S7-400 modules require the use of a modular backplane (the S7-300 use a support rack and bus connectors).

So if you are asking how to replace physically one S7-300 CPU with a S7-400 CPU, basically it cannot be done.

If however you plan to use the I/O modules of the S7-300 as part of a S7-400 setup, then either the S7-300 CPU can be setup as a Profibus-DP slave, replaced by an IM153-2 slave interface module on Profibus, or data can be exchanged between the 2 CPUs through Ethernet (CP343-1/CP443-1, or Profinet connections). Note that there will be limitations on the amount of data exchanged, S7-300 CPs for example will be hard to connect on slave modules.

Please come back with more preciwe info on what you are trying to do so we can comment with better understanding.

Hope this helps,
Daniel Chartier

Hi,

Hardware:
1. Note the number of DI/DO/AI/AO used in S7-300
2. Get the S7-400 I/O to match the S7-300
3. Configure Hardware accordingly.
Generally, you would not have a problem with CPU memory size as S7-400 has larger capacity.

Software:
1. Check the standard FC/FB used. You might need to reprogram.
2. If SFC/SFB are used, you would need to reprogram.
3. Check the OB used. You might need to reprogram.
4. Rewire IO if required.

Hope this would help.