Connecting Multiple MSP430 USB I/F's Together

Hello All,

I am working on a design in which we have 3 MSP430's - all with USB modules - and we want to connect all of the USB I/F's together.

We want to do this for a couple of (obvious) reasons, BSL and normal USB communications.

I think we have worked out the solution for PUR - but I was wondering if any one of you have done this already.

According to Ch. 7 of the USB 2.0 spec (you can download for free off of USB.org) - as long as the connect timing requirements are met - I think it is OK to wire-OR all of the connections together.  We've added control circuitry that will guarantee power and PUR will sequence correctly to invoke BSL; and this same control should let all 3 USB connections be valid.

On a previous board turn we tried wire-OR'ing all of the signals together and sharing the PUR line per processor; but it only worked for the 1st processor that became valid and I am pretty sure we were violating the connect timing requirement; which is of course why it didn't work.  I just wanted to ask if anyone else have tried doing this in their design - and what challenges they had.

Obvious benefits here are being able to use USB BSL (preferred) and having USB communication working on all 3 processors.

Thanks In Advance,
johnw