Expansion Bus?

[Guest Phuong Nam]

Dear, I have just been survery about expansion bus of S7-200. Has anyone had any info about the expansion bus? Would you help me! Best Regards Nam

[Crossbow]

The expansion bus is proprietary. Only Siemens knows how it works. Why would you need to know anyways? Just plug in the modules and away they go, no configuration or anything...

[Guest PN]

I want to know basic information: the bus is serial or parrallel ? sync or async? voltage level? so I can drag on the bus as long as possiple. Pls help me!!! Thanks.

[Guest Ken M]

I'm inclined to agree with Chris. You can only add Siemens' modules to the bus, so stick by their rules. As far as I know the main limitation on the S7-200 is the total power budget of all the modules. A couple of Ethernet modules will consume that budget much more quickly than several digital input modules. You can't change whether it's sync/async or serial/parallel so why care? Regards Ken

[Guest sinnaig]

As far as I know the limitation on the S7-200 is not only the total power budget of all the modules but and the number of the modules...only 7max. for s7-200. isn't this true???

[Crossbow]

Each Siemens S7-200 has the capability to output a certain amount of 5VDC across the bus. It is true that their stance is the S7-221 is non-expandable, the S7-222 can have a max of two modules, and the S7-224 and S7-226 can have a max of 7. This is basically a limitation of the power on the bus, but they ave chosen to limit in their software to prevent a user from exceeding the limits. They sell a small extension cable, which will allow you to take a long S7-200 bus and break it onto two separate DIN rails, but it's under 1 meter and the S7-200 bus is not designed for such things as remote modules or distributed I/O. If you're looking for distributed capabilities, try AS-Interface or Profibus. S7-200 can master AS-Interface or slave on Profibus. Other option is to have multiple S7-200 units with Ethernet and make them talk to each other over Ethernet.