siemens plc communication

Hi dears,
What is diffrence between MPI and PPI cables? Can we use PPI cable inplace of MPI cable?

I think the PPI cable is only for S7-200..

Yes PPI cable for s7 200 but my question is IF both PPI and MPI protocol is RS485 then why we should not use PPI cable inplace of MPI cable

Heres an extract from the siemens forums...

MPI is PROFIBUS based and is using the regulations of PROFIBUS too... So you have max. 256 Byte long telegrams with Header and Taylor like PROFIBUS.

PPI is RS485 based and closely to PROFIBUS but due to the smaller performance for Communication the PPI Telegramm can contain gaps within the Data... so you have usually no defined Telegramlength like you would need it for PROFIBUS. Due to this MPI and PPI do not work together.

This is rough and someone here can probably shed more light on it.

You can use a MPI usb cable instead of an PPI cable but not the other way around.. The usb mpi cable must be a newer version more info look at siemens

A little more info....

http://www.plctalk.net/qanda/showthread.php?t=37010