Experimental Physics and
Industrial Control System
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| <== Date ==> | <== Thread ==> |
|---|
| Subject: | Re: Question on transition modules |
| From: | Andrew Johnson <[email protected]> |
| To: | "Chestnut, Ronald P." <[email protected]> |
| Cc: | [email protected] |
| Date: | Mon, 07 Jun 2004 12:33:19 -0500 |
In our group at SLAC we are using some MV167/MV177 and some PPC 2700 VME controllers. Each class has its own transition module. Rumor has it that using the wrong transition module can damage the CPU. Since there seem to be active components on the transition module, this is entirely believable.
There are active components on the MVME761 transition module, because there were not enough pins available on the P2 connector to pass through all of the signals that MCG needed, so they now multiplex some of the serial signals and have to demultiplex them again on the transition module. They also moved the RS232 serial drivers off the CPU onto the transition module, and for COM3 and COM4 you get to pick what kind of signals you want by buying and plugging in the appropriate daughter board containing these driver chips. There might be something relating to the network on there as well...
We also have some older VME crates with homebrew "transitions"; these crates all currently have MV167/MV177 modules. The interface is entirely passive, with connections to the backplane and to external connectors for one console port and ethernet. The advantage of these crates is that one can actually get modules in without a mallet, and that many are available. The layout of the crate precludes using the commercial 2700 transition module without moving the power supply around.
You can buy versions of the MVME2700 that will plug into a MVME712 transition module, but you only get 10MB networking if you do that, and I think there may be some other limitations which I've forgotten about; presumably you've already discounted this option.
Before I fry an MV2700, I would like to know if this purely passive "transition" solution has the possibility of actually harming the CPU.
As I said above, you probably won't be able to use a purely passive transition solution because of the demultiplexing and serial driver functions that are on the MVME761. However you could build your own transition module, or possibly even buy an alternative to the Motorola module - here at APS we build our own transition modules in a VME form factor, which sit in the adjacent slot and connect to the CPU card via a P2 ribbon cable. We have requirements for optical connections which you'd probably not want, but this shows what's possible if your need is great enough.
- Andrew -- Dear God, I didn't think orange went with purple until I saw the sunset you made last night. That was really cool. - Caro
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- Question on transition modules Chestnut, Ronald P.
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