siemens newbie here, questions about OP27 and s7-300

hello everyone,

i m trying to rebuild an old machine sitting idle for many years. it has a OP27 panel and 2 CPUs (314 and 316). i did connect the plcs and manage to upload programs but since i couldnt manage to find a way to get symbol tables, comments and the old program was written in STL its all nonsense for me. the machine will get a quite work over as mechanically aswell so i need to program it from scratch anyways. this will be my first siemens apllication beside a couple of simple LOGO projects so bear with my stupid questions
here i go;

1- how to configure network in step7?
phisically cpu 314 and cpu 316 are connected each other via profibus ( a purpleish cable) and OP27 is connected to cpu 314 with profibus ( a blue cable ). is it correct to make one MPI line and connect both CPUs and OP there? addresses 2 and 4 for CPUs and 1 for OP27

2- how to connect OP27?
can i dowload programs with same mpi adapter i use for CPUs or do i need a different cable for that? if the second case is true i have found some cable connections for 15 pin - 9 pin, 3-3, 4-2 , 12-5. is this pin connection correct?

1. That seems correct.
Profibus cable is purple, and for a small MPI network you descibe you use Profibus cable and connectors. The connection will be daisy-chained via the profibus connectors. It is a worry that one of the cables is blue. If it is not a real profibus cable it may still work since MPI @ 187.5 kbps is quite forgiving.

2. You can download to the OP27 via MPI, or serially via RS232 and the IF2 port.
Here is a description of the cable needed for serial download:
http://www.plctalk.net/qanda/showpost.php?p=249583&postcount=3
The pins you described seems correct.