ben@epmooch.UUCP (Rev. Ben A. Mesander) (02/18/91)
>In article <drues.666917751@pv320a.vincent.iastate.edu> drues@iastate.edu (Michael E Drues) writes: >Can anyone tell me what ASCII code for "BREAK" is??? >I can't find it in ASCII table I have. > >Thanks, >mike > >-- >Michael Drues Dept. of Biomedical Engineering >Internet:drues@iastate.edu 1146 Veterinary Medicine >BITNET:v2.med@isumvs.bitnet Iowa State University >Office:(515)294-6520(or 4-1771) Home:(515)233-5652 Ames, Iowa 50011 If you're asking about sending a "break" over a modem line, it is not an ASCII character. A break simply holds the RS-232 send line active for a "long" time, usually ~1 sec, and is *not* a normal character consisting of start, stop, and data bits. Terminal programs usually have an option to set the length of a "break." Remote computers usually have thier own "break" characters to abort applications. On UNIX and MSDOS machines, it is a CTRL-C. On Primes, it is a CTRL-P. On Amigas it is a CTRL-C or a CTRL-D depending on the application. TRS-80's use a CTRL-A for break. CP/M uses a CTRL-C... -- ben@epmooch.UUCP ben%servalan.UUCP@uokmax.ecn.uoknor.edu {chinet,uokmax}!servalan!epmooch!ben (Ben Mesander) War in gulf: newpath 288 396 216 0 360 arc 288 612 moveto 288 180 lineto 288 396 moveto 136 244 lineto 288 396 moveto 440 244 lineto 36 setlinewidth stroke showpage
drues@iastate.edu (Michael E Drues) (02/19/91)
Can anyone tell me what ASCII code for "BREAK" is??? I can't find it in ASCII table I have. Thanks, mike -- Michael Drues Dept. of Biomedical Engineering Internet:drues@iastate.edu 1146 Veterinary Medicine BITNET:v2.med@isumvs.bitnet Iowa State University Office:(515)294-6520(or 4-1771) Home:(515)233-5652 Ames, Iowa 50011
papa@pollux.usc.edu (Marco Papa) (02/19/91)
In article <drues.666917751@pv320a.vincent.iastate.edu> drues@iastate.edu writes: >Can anyone tell me what ASCII code for "BREAK" is??? >I can't find it in ASCII table I have. There is NO ASCII code for BREAK. That's why you didn't find it. Break is a line condition, not a ASCII code. -- Marco -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= "Xerox sues somebody for copying?" -- David Letterman -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
thad@public.BTR.COM (Thaddeus P. Floryan) (02/19/91)
In article <drues.666917751@pv320a.vincent.iastate.edu> drues@iastate.edu writes: >Can anyone tell me what ASCII code for "BREAK" is??? >I can't find it in ASCII table I have. There is NO code for ``BREAK'' since it is not a character but, instead, a continuous (typically 100 to 300 mS) "condition" on the line. Some OLD software I've seen would attempt to simulate a BREAK by setting the baud temporarily to, say, 50, then sending an ASCII ``NULL'' char, but that is a kludge. Thad Floryan [ thad@btr.com (OR) {decwrl, mips, fernwood}!btr!thad ]
ccplumb@rose.uwaterloo.ca (Colin Plumb) (02/19/91)
drues@iastate.edu wrote: >Can anyone tell me what ASCII code for "BREAK" is??? >I can't find it in ASCII table I have. Break is not part of ASCII; it's more part of RS232. Well, actually, it makes sense in most asynchronous serial protocols, but there aren't very many that aren't descendants (some legitimate; most bastard) of RS232. The details: When sending data over an asynchronous line (like RS232), the bits (8, usually) of a character are surrounded by start and stop bits to synchronise the receiver. When the line is idle, it transmits a continuous stream of 1's. When a character is to be sent, it's preceded by a 0 bit, which signals the receiver that something is coming. The receiver has been sampling the line at typically 16 times the bit frequency (38400 times a second for 2400 baud) looking for a 0 signal. When it gets it, it waits half a bit time and checks again, to make sure the 0 bit is really there. Then it waits one bit time, reads the bit, waits one bit time, reads the next bit, etc. At the end of the last bit, it waits one more bit time and checks the stop bit (which must be a 1 signal) and goes back to checking 16 times per bit for a 1->0 transition. This way, the received bits are the signal measured on the line in the middle of each of the transmitted bits. If the receiver's clock is not at quite the same speed as the transmitter's, as is inevitably the case, then the times at which the receiver measures the bits will drift away from the centre. As long as you don't get more than 1/2 a bit drift in a single character, the receiver will still be measuring the right bits and will get the right values. It resynchronises to the leading edge of the start bit every character, so error does not build up forever. If, at the end of one character, the receiver does not see a 1 level, it can't accurately find the change to 0 level that indicates the next character and so it signals a "framing" error. Note the need for a full stop bit. If the receiver was running fast, it might have sampled early in the last data bit and needs to wait that entire data bit before the line is clear (1) again. If the receiver was running slow, it might have sampled almost the end of the last data bit, and waiting the minimum full bit time will place it at the end of the stop bit. If the stop bit were less than a bit, it would be missed. If your clocks are more accurate than this, you can economise a little, but it's not really worth it. The best use of more accurate clocks is to send more bits between start and stop, but as a practical matter, it's hard to find chips which will do this. Anyway, due to the presence of stop bits, if there are 8 data bits, there are at most 9 bit times (start + 8 data bits of 0) of 0 signal allowed in a row. Rules are made to be broken, so you can break this rule to sens a special signal (a break) to the receiver. It is not a normal character, although it looks like a 0 byte with a framing error. Breaks are typically at least 2 characters long, and often much longer than that, and are frequently used to reset a receiver somehow or return it to a sensible state. If you look at any serial device deriver or serial chip, you'll see some bit or command to send a break, but this bit does not correspond to normal data... it's abnormal, just as there is no touch tone frequency corresponding to hanging up a telephone. -- -Colin
coburn@clo.enet.dec.com (John T. Coburn) (02/19/91)
In article <drues.666917751@pv320a.vincent.iastate.edu>, drues@iastate.edu (Michael E Drues) writes...
:Can anyone tell me what ASCII code for "BREAK" is???
:I can't find it in ASCII table I have.
:
That's because a BREAK is not an ASCII code - it is a line condition ie it is a
mark or space (I forget which) on the serial line for a defined period of time
that is greater than 1 bit time.
:Thanks,
:mike
:
:--
:Michael Drues Dept. of Biomedical Engineering
:Internet:drues@iastate.edu 1146 Veterinary Medicine
:BITNET:v2.med@isumvs.bitnet Iowa State University
:Office:(515)294-6520(or 4-1771) Home:(515)233-5652 Ames, Iowa 50011
--------------------------------------------------------------------------------
John Coburn !Email:
Digital Equipment Corporation ! coburn@clovax.enet.dec.com -or-
Enterprise Integration Services ! coburn%clovax.enet@decwrl.dec.com
Cleveland, Ohio ! ...!decwrl!clovax.enet!coburn
================================================================================peterk@cbmger.UUCP (Peter Kittel GERMANY) (02/19/91)
In article <1991Feb19.032422.26230@watdragon.waterloo.edu> ccplumb@rose.uwaterloo.ca (Colin Plumb) writes: >drues@iastate.edu wrote: >>Can anyone tell me what ASCII code for "BREAK" is??? >>I can't find it in ASCII table I have. > >Break is not part of ASCII; it's more part of RS232. Well, actually, >it makes sense in most asynchronous serial protocols, but there aren't >very many that aren't descendants (some legitimate; most bastard) of >RS232. > > [ lots of detailed explanation deleted ] Hmm, I hardly dare to step in here because so many people already stated that there is no ASCII code for BREAK, BUT: In most systems I know, a Ctrl-C serves as a break signal. Now, for this you can indeed give an ASCII value, it's 3. For beginners: If you press Ctrl and a letter key, the system will deliver the code of the key minus 64 (at least normally :-). So, Ctrl-A gives a 1, and Ctrl-Z gives a 26 (often used as EOF in the CP/M and MS-DOS world). -- Best regards, Dr. Peter Kittel // E-Mail to \\ Only my personal opinions... Commodore Frankfurt, Germany \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk
billy@phoenix.pub.uu.oz.au (Jeff Coleman) (02/21/91)
There is a bit of a description on the workings of achieving break on the AMIGA in the RKM Inc+Autodoc manual under serial.device ... obviously you are meant to use the serial device to do the break for you.. but there is enough information there (and with the knowledge of custom chips) to do it at a lower level. & mind you i'm not advocating it! &