analog MUX should work take 74HC(T)4051 cheap 8:1 MUX, supply it with +/- 5V ON-resistance about 50 Ohms
and 74HC4052 dual 4:1 MUX take 4052 -- 4051 -- 4051 paths 1 -- 2(4) -- 16 -- 128 //Alois > More and more sounds like a job for an FPGA. The logic flow appears > simple enough and I/O availability wouldn't be a problem. There's an > investment in hardware and a learning curve, however. > > Tony > > -----Original Message----- > To: Multiple recipients of list CHIPDIR-L <[email protected]> > Sent: Tue, 23 Aug 2005 09:04:22 -0800 > > Hi, > > It's a calibration system, and as such it requires high reliability. > > Networking and addressing leaves the system open to problems such as > if one RS485 chip goes short circuit, for example, it will bring the > whole network down and screw up the (lengthy) calibration process > > Therefore IT MUST be designed this way, unless you can think of > anything > better > > Separating each channel isolates unit specific problems to just that > channel > > > > -----Original Message----- > Declan Moriarty > Sent: 23 August 2005 17:49 > To: Multiple recipients of list CHIPDIR-L > > > Recently, Somebody Somewhere wrote these words > > Hi, > > > > Thanks. > > > > I think I should have been more specific. > > > > We've got an RS485 comms pair, which we want to multiplex between > > 120 RS485 pairs. > > > > I.e. 120 channels to 1 (or 240 to 2 in terms of actual wires). > > > > Ive seen a 32 channel analogue switch from Analogue devices, but im > > unsure as to whether an Analogue switch will be ok? > > > > To quote the Irishman who was asked for directions to somewhere: > > "You know... If I was you, I wouldn't start from here at all!" > > You are never going to stand up 1-->120 in an RS485 link without such > heartache as to justify a sane design. What's your baud rate? You > would also need sample & holds everywhere. Network the things and > address them. Start over, my friend. > > Imagine when you get the complaint "Channel 87 goes intermittent after > about 5 minutes" How will you sort that? > > BTW, the trick with analogue switches is never bring the input below > the negative rail. > > > > -- > > > > With best Regards, > > > Declan Moriarty. > -- > Author: Declan Moriarty > INET: [EMAIL PROTECTED] > > Fat City Hosting, San Diego, California -- http://www.fatcity.com > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message to: > [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the > message BODY, include a line containing: UNSUB CHIPDIR-L (or the name > of mailing list you want to be removed from). You may also send the > HELP command for other information (like subscribing). -- Author: > Darren Logan > INET: [EMAIL PROTECTED] > > Fat City Hosting, San Diego, California -- http://www.fatcity.com > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message to: > [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the > message BODY, include a line containing: UNSUB CHIPDIR-L (or the name > of mailing list you want to be removed from). You may also send the > HELP command for other information (like subscribing). > > > -- > Author: > INET: [EMAIL PROTECTED] > > Fat City Hosting, San Diego, California -- http://www.fatcity.com > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message to: > [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the > message BODY, include a line containing: UNSUB CHIPDIR-L (or the name > of mailing list you want to be removed from). You may also send the > HELP command for other information (like subscribing). - - - - - - - - - - - - - - - - - - - - - - - - - - Alois Bauer WORK Microwave GmbH Raiffeisenstr. 12, D-83607 Holzkirchen, Germany Tel. {+49} (0)8024-6408-0 / FAX (0)8024-640840 -- Author: Alois Bauer INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
