hello Hisham;
You will find in the following link the manual for communications between WinCC Flexible 2008and 3rd party PLCs, including the A-B family:

http://support.automation.siemens.com/WW/view/en/18797249
Note that there are similar manuals for other versions of WinCC Flexible, on the same support webpage, if required.

Introduction

This section describes the communication between an HMI device and Allen-Bradley controllers of the types SLC500, SLC501, SLC502, SLC503, SLC504, SLC505 (simply called SLC below) and PLC5 and MicroLogix.

With these controllers, the connections use protocols that are specific to the controllers.

• DF1 - point-to-point connection
• DH+ over KF2 module and DF1 multipoint connection
• DH485 - multipoint connection (NOTE: except PLC-5)
• DH485 over KF3 module and DF1 multipoint connection

The next sections describe cables,interface assignments, driver configuration and register types that can be used.
It should provide most of the data you need.
Hope this helps,
Daniel Chartier