transmitting BREAK
Howard Hull
hull at hao.UUCP
Wed Apr 11 06:34:49 AEST 1984
I take exception with respect to Rob Warnock's (!fortune!rpw3) statement:
Sorry, Mcferrin, Nelson is right.
While it is true that a <NUL> is all zeroes and a <DEL> is all ones,
>>>>>the idle state of RS-232 data lines is MARK == ONE == +Volts. A start
>>>>>bit is a SPACE == ZERO == -Volts, and stop bits are ones. Therefore,
if you want a big wide BREAK == "long space" == "long zeroes", better
send a slow <NUL>.
doesn't seem to ring true for the RS232 coming out of pin 2 of my terminal.
An oscilloscope shows the idle state at -12 volts (MARKING) is the level for
logical ONE ; the +12 volt state (SPACING) is for logical ZERO. The additional
information can be added to Jerry Aguirre's contribution (thanks for accurate
graphics, Jerry):
-12V ------ ......................................------//-- MK
| start . . stop | next
0V idle | bit . your character with parity . bit | start
1 | 0 . . 1 | bit
+12V -------...................................... ----- SP
So you can either be positively logical, or stand on your head when you look
at your oscilloscope. Howard Hull !hao!hull
More information about the Comp.unix
mailing list