wehr@fmeed1.UUCP (Bruce Wehr) (05/23/90)
In article <1990May22.165409.3727@murdoch.acc.Virginia.EDU>, sdm7g@dale.acc.Virginia.EDU (Steve D. Majewski) writes: > What is VXI bus ? Vme eXtensions for Instrumentation > Is this a (standardized) variant of VME ? Yup. > - or is this a faster IEEE-488 type of interface ? Nope. VXI is an extension of the VME bus to accomodate instruments-on-a-card. There are different types of VXI controllers. You can have external boxes that talk to the cage through a 'Slot 0' interface equipped with an IEEE-488 interface. Communication to the cards is slow (the interface must translate high-level ASCII IEEE-488 commands to register-level commands), but the controller is easily exapanded. Or, you can have controllers that plug in the cage. This gives you register-level access to your cards (they appear in the address space of the controller), but your controller is not very easily expanded. One drawback to VXI is that a cage typically contains 13 slots, and if you need more, IEEE-488 is (was?) the only way to daisy-chain cages. I've heard of a thing called MXI (I was told that stands for Multiple eXtensions for Instrumentation) that will allow transparent daisy-chaining of multiple cages. I've also heard that MXI allows external controllers to get register-level access to the cards. Talk about the best of both worlds! I'm trying to find out more about MXI. Any takers? -- Bruce Wehr (wehr%dptc.decnet@srlvx0.srl.ford.com) (...!mailrus!sharkey!fmeed1!wehr) (wehr%fmeed1.uucp@mailgw.cc.umich.edu) Ford Motor Company - Electronics Division 17000 Rotunda Drive, ETC Room LN081, Dearborn, Michigan 48121 (313)845-3039
rjn@snowbird.LABS.TEK.COM (Jim Nusbaum) (05/26/90)
In article <6630@fmeed1.UUCP> wehr@fmeed1.UUCP (Bruce Wehr) writes: > >VXI is an extension of the VME bus to accomodate instruments-on-a-card. >There are different types of VXI controllers. You can have external >boxes that talk to the cage through a 'Slot 0' interface equipped with >an IEEE-488 interface. Communication to the cards is slow (the >interface must translate high-level ASCII IEEE-488 commands to >register-level commands), but the controller is easily exapanded. Or, >-- > Bruce Wehr (wehr%dptc.decnet@srlvx0.srl.ford.com) One slight clarification. Communication to VXI slot 0 controllers does not have to be via GPIB. It can be anything you want (serial, ethernet, etc.) and therefore does not have to be slow. MXI bus is pushed by National Instruments and I think their catalog has a discussion of it. -- Jim Nusbaum, Computer Research Lab, Tektronix, Inc. [ucbvax,decvax,allegra,uw-beaver,hplabs]!tektronix!tekchips!rjn rjn@tekchips.labs.tek.com (503) 627-4612