communicating w/ ET200S with IM151-7 cpu

Is there any other option to talking/programming a stand alone ET200S with IM151-7 cpu without buying the $500+ USB-to-MPI adapter?! I got the MPI cable thinking I could program the controller via my laptop's serial port... then I realized it is a 422 based protocol and an adapter of some sort is required. It's almost the same cost as the controller itself!?! Any help?

422 "protocol" ???
RS422 is an electrical standard, not a protocol.
The MPI/DP port on the IM151-7 uses RS485 not RS422.
If you have the MPI adapter for the serial port on the PC, then it can be used for programming the IM151-7. If not you have to invest in something that can speak "MPI", for example the USB adapter you mention.

Oh, by the way, there is a new CPU for the ET200S, the IM151-8.
It has ethernet in stead of MPI/DP, 128kB memory, a faster CPU, and almost the same price as the IM151-7. So with this one you dont have to pay for an MPI adapter.

There are a few catches though: It has not been released yet, despite it has been announced for june. And you cannot program it with STEP7 LITE (in case you are using that).

Just thought I would mention it.

thanks for the info. I heard about that new cpu from my siemens rep... but regarding comm with the 151-7: can I use the USB / PPI Multi Master Cable?? I do have access to one of those, but it seems that it only works with the S7-200s, however my rep told me it would work and that I needed to D/L a driver.. but I cannot find said driver on their website... still no talkie.

You definitely cannot use the PPI cable with the IM151-7.
The cheapest possibility is the USB adapter.

If you are at the point where you have to make a "strategic" decision (which PLC type to use for a new product for example), then I recommend that there is "ethernet" somewhere in your equation. MPI, bless it, is to my opinion heading for obsolescence.