Sdi-12 timing, Figure 31, Timing diagram – Vaisala WXT520 User Manual
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Appendix B __________________________________________________________ SDI-12 Protocol
VAISALA______________________________________________________________________ 159
SDI-12 Timing
shows a timing diagram for a SDI-12 command
and its response. The tolerance for all SDI-12 timing is ±0.40
milliseconds. The only exception to this is the time between the stop bit
of one character and the start bit of the next character. The maximum
time for this is 1.66 milliseconds, with no tolerance.
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A data recorder transmits a break by setting the data line to spacing
for at least 12 milliseconds.
-
The sensor will not recognize a break condition for a continuous
spacing time of less than 6.5 milliseconds. The sensor will always
recognize a break when the line is continuously spacing for more
than 12 milliseconds.
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When receiving a break, a sensor must detect 8.33 milliseconds of
marking on the data line before it looks for an address.
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A sensor must wake up from a low-power standby mode and be
capable of detecting a start bit from a valid command within 100
milliseconds after detecting a break.
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After a data recorder transmits the last character of a command, it
must relinquish control of the data line within 7.5 milliseconds.
0505-218
Figure 31
Timing Diagram