markw@remote.halcyon.wa.com (Mark Ward) (07/28/90)
I'm looking for a few cheap ethernet transceivers (isn't everyone). I almost asked about using the 15 pin cables, but I caught the other messages in time :-)... Where can I get a book that actually says blah blah chip so an so does this, and in the xceiver, we use a silly matching transformer and a couple whatevers and gouge you big bucks? I mean isn't it possible to build my own transceivers? Almost did it with appletalk (they sold you a diagram for $20), but now the boxes are so cheap I don't need to worry about it... All books I've ever seen about networks fall into one of two categories: (1) "well gosh, if you really need to hook them together, go pay a guy who knows what he's doing to do it for you...", or (2) "Well, here's this impossible description of layers that you'll think easy once you get a clue, but we're not gonna help you get that far, and if you want to know about the hardware, get a job at a place building them" I desperately desire a book that will quence my thirst for knowledge on transceivers, ethernet, layers, ftp, tcip, amd ethernet controller chips, the pin-outs of those silly 15 pin cables..... -mark
bruce@balilly.uucp (Bruce Lilly) (07/31/90)
In article <6Xc1m12w162w@remote.halcyon.wa.com> markw@remote.halcyon.wa.com (Mark Ward) writes: >I'm looking for a few cheap ethernet transceivers (isn't everyone). >I almost asked about using the 15 pin cables, but I caught the other >messages in time :-)... Where can I get a book that actually says >blah blah chip so an so does this, and in the xceiver, we use a silly >matching transformer and a couple whatevers and gouge you big bucks? You don't *really* expect to find a book that says *that*, do you? >I mean isn't it possible to build my own transceivers? Almost did it >with appletalk (they sold you a diagram for $20), but now the boxes are >so cheap I don't need to worry about it... Yes, it's possible, however: 1) Ethernet(tm) runs at 10 Mb/s, so experience with high-frequency circuit design is essential. Building the unit on a PC board with adequate grounding (perhaps even a ground plane) is necessary. 2) You'll want some type of box or enclosure, which will need to accomodate the 15-pin D connector and a BNC connector (assuming thinnet -- don't even think about making your own tap for thick cable). 3) The cost of the components, enclosure, connectors, PC board fabrication, and your time to design, build, and debug the units will probably total as much as or more than the price of a commercial unit. >I desperately desire a book that will quence my thirst for knowledge on >transceivers, ethernet, layers, ftp, tcip, amd ethernet controller chips, >the pin-outs of those silly 15 pin cables..... IC's are described in ``Handbook of LAN Technology'' by Paul J. Fortier, published by McGraw-Hill ($64.95). The pinout of the 15-pin cable is shown in ``Keeping the Link'' by Martin Nemzow, also published by McGraw-Hill ($39.95). (No, I don't work for McGraw-Hill) There are other books; check your local library or technical bookstore, as well as application notes from the IC manufacturers. Of course, you'll probably find that it's simpler, quicker, and less costly to simply purchase a unit. >-mark -- Bruce Lilly uunet!vmp!sonyd1!blilly!balilly!bruce
rpw3@rigden.wpd.sgi.com (Rob Warnock) (08/04/90)
In article <1990Jul31.031438.19090@blilly.UUCP> bruce@balilly.uucp (Bruce Lilly) writes: +--------------- | IC's are described in ``Handbook of LAN Technology'' by Paul J. Fortier, | published by McGraw-Hill ($64.95). The pinout of the 15-pin cable is | shown in ``Keeping the Link'' by Martin Nemzow, also published by | McGraw-Hill ($39.95). (No, I don't work for McGraw-Hill) There are other | books; check your local library or technical bookstore, as well as | application notes from the IC manufacturers. +--------------- Better still would be to read the Ethernet Specification itself (*not* 802.3!). It's quite readable, has all the actual requirements for voltages, impedances, drive currents, rise times, etc., and even has sample circuits for driving and receiving the 15-pin interface. WARNING! The sample circuit for a transceiver-cable receiver has a bug, which is in both Version 1.0 and Version 2.0 of the spec, and I have also seen it in the schematics for at least one of the DEC-manufactured transceivers. The "data valid" output of the circuit is mistakenly connected to the *center-tap* of the terminators for the incoming signal. [Boo! Hiss!] Thus common-mode signals are sent backwards up the cable. [When copying this circuit, don't do it that way. ;-} ] A friend of mine at Xerox once confided that they knew the bug was there, but couldn't change it in time because of the long review/approval cycle through the DEC/Intel/Xerox loop. When Version 2.0 was being edited, they'd forgotten just what the bug was, and removed the wrong wire, leaving only the *bad* connection! It's pretty obvious what "data valid" *should* be hooked to -- just look for a gate with no output connections. Otherwise, and on the whole, the Ethernet Spec is a *very* good guide. You also should look at the data sheets for some of the transceiver chips, such as the ones made by AMD or National. I believe these have sample circuits for complete transceivers, including hints/warnings about circuit layout to meet the stringent stray capacitance and isolation rules. -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311