Campbell Scientific MD9 Coax Multidrop Interface - Manual (Page 15)

B-1
Appendix B. Break/Address Timing
A BREAK consists of continuous spacing for time greater than 10 times the
inverse of BR (baud rate). The BREAK is followed by a marking period and
single byte ADDRESS. The marking time must be greater than one times the
inverse of BR and the marking time and ADDRESS must be completed within
100 msec.
This is to say that a 9600 baud, the BREAK must be greater than 1.1 m sec
followed by marking for 105 usec. The 8 bit single character ADDRESS (least
significant bit first) is then completed within 100 msec after the end of
BREAK.
FIGURE B-1. Break/Address Timing Diagram