Are you terminating the lines at one end or at both ends? My recollection is that they should be terminated at one end only.
On Thu, 19 Sep 2002 03:53:29 -0800 Elbert Smit <[EMAIL PROTECTED]> wrote: > Hello Chipdir members, > > We are using LTC485 RS-485 transceivers and found some strange behavior. > > We have a test setup with two devices, one using a Sipex RS232/RS485 > (selectable) transceiver in a industrial PC, and one of our own devices, > using the LTC485. > > These two devices will only communicate if we remove the termination > resistor of 120 ohm at one side, leaving the bus unterminated. > > When the resistor is placed, the voltage swing of the A and B channel is > still about 2 Volt, which should be sufficient, according to the RS-485 > documentation I have. Only differences below 200mV are undefined. However, > the 2 Volt voltage is not enough to operate for some of the devices. We > tried several LTC485's and found out that some of them worked fine with > termination, but some didn't. Testcable length is an awsome 50 cm ;-) > > Any ideas or clues? > > Kind regards, > > Elbert Smit > -- > Author: Elbert Smit > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > 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: Peter Vogel INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- 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).
