Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site oliveb.UUCP Path: utzoo!watmath!clyde!burl!ulysses!harpo!ihnp4!zehntel!hplabs!oliveb!jerry From: jerry@oliveb.UUCP (Jerry Aguirre) Newsgroups: net.unix Subject: Re: transmitting BREAK Message-ID: <323@oliveb.UUCP> Date: Mon, 9-Apr-84 16:10:25 EST Article-I.D.: oliveb.323 Posted: Mon Apr 9 16:10:25 1984 Date-Received: Wed, 11-Apr-84 05:23:20 EST References: <16800@sri-arpa.UUCP> <3864@genrad.UUCP> <941@inuxc.UUCP> Organization: Olivetti ATC, Cupertino, Ca Lines: 30 With regard to sending a NULL at 50 BAUD to simulate a break: mcferrin@inuxc.UUCP (P McFerrin) says: A NULL is all zero's. You really want a DEL (0377). Actually you do want a NULL. The idle state for an rs232 line is the mark or all ones state (for "historical" reasons which I suspect date back to the days of current loop). A break consists of forcing the line into the all zero state for more than one character time. ------ ......................................------//-- | start . . stop | next idle | bit . your character with parity . bit | start 1 | 0 . . 1 | bit -------...................................... ----- The only thing sending a 0377 would do is maybe send a break because of the zero start bit. I have tried the approach of sending a NULL at 50 BAUD and it works well enough to toggle the 1200/300 BAUD rate. Actually an '@' (0100) will work nearly as well. But keep in mind that a break is not always a break. Some hardware requires a longer break before it will take notice. Our PDP-11/70 will toggle BAUD rate on a 50 BAUD NULL but our Micom port selector will not break the connection. It apparently requires a longer break. Check out any modem or other data communication equipment that requires a break. They may have a minimum break time specified in the specs. Jerry Aguirre {hplabs|fortune|ios|tolerant|allegra|tymix}!oliveb!jerry