kieffer@UNCAEDU.BITNET (06/24/87)
we are running several Vax systems under VMS, each is connected to a Develnet dataswitch via RS232 connections. We noticed that the Vaxes are playing with the DTR lines when the connection is idle, ie no session in effect over a specific port. However, everytime DTR is cycled the network thinks that the computer is trying to establish an outgoing call (with kermit for example) but since there is no activity, the network eventually times out. The only real inconvenience is the fact that the event is logged on the network console printer and we go through boxes of paper every week. (the cycle lasts about 30 seconds). The device is a DZ, but it has happened on other models too. It does not seem to happen under Unix, God only knows why. Is there any way to stop this yo-yo behaviour? Rom Kieffer University of Calgary Alberta Canada
oberman@LLL-ICDC.ARPA ("Oberman, Kevin") (06/25/87)
>We are running several Vax systems under VMS, each is connected to >a Develnet dataswitch via RS232 connections. >We noticed that the Vaxes are playing with the DTR lines when the >connection is idle, ie no session in effect over a specific port. >However, everytime DTR is cycled the network thinks >that the computer is trying to establish an outgoing call (with kermit >for example) but since there is no activity, the network eventually times out. >The only real inconvenience is the fact that the event is logged on >the network console printer and we go through boxes of paper every week. >(the cycle lasts about 30 seconds). >The device is a DZ, but it has happened on other models too. It does not >seem to happen under Unix, God only knows why. > >Is there any way to stop this yo-yo behaviour? There has been a lot of discussion on exactly how VMS handles modem control signals in the past. I won't try to repeat most of it. The reason the DTR line toggles on idle terminals is that the DZ-11 does not have any real modem control capability. Among other things, it does not have any way to detect a hangup properly. To handle this, the SYSGEN parameter TTY_SCANDELTA is used to periodicly toggle the DTR line on modems that don't have CARRIER asserted. For more complete details, see the I/O Users Reference Manual, Vol. 1, ppg. 8-11 thru 8-16. The above applies to DZ11s, DZV11s, and VAX 8200 serial lines (as per table 8-1). This whole thing gets VERY messy because of the wide variety of hardware and line combinations that must be handled. The TTDRIVER has a long state table to take care of it. In the past the flow of this table has been posted. Even that din't make things obvious. Good luck! R. Kevin Oberman Lawrence Livermore National Laboratory arpa: oberman@lll-icdc.arpa (415) 422-6955 Disclaimer: Neither my employer nor myself can take resposibility for the accuracy of this information. I believe it is correct, but if it's not I can only say "Sorry". I'm a rotten typist and a worse speller, so forgive any silly errors. ------