The exception to this is the time between the stop bit of one character and the start bit of
the nex
t character. The maximum time for this is 1.66 ms, with no tolerance.
• A data recorder transmits a break by setting the data line to spacing for at least 12 ms.
• The sensor does recognize a break condition for a continuous spacing time of less than
6.5 ms. The sensor will always recognize a break when the line is continuously spacing
for more than 12 ms.
• When receiving a break, a sensor must detect 8.33 ms of marking on the data line
before it looks for an address.
• 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 ms after detecting a break.
• After a data recorder transmits the last character of a command, it must relinquish
control of the data line within 7.5 ms.
Figure 41 Timing Diagram
• A
fter receiving the break and the command, the addressed sensor sets the data line to
marking at 8.33 ms and then sends the response (tolerance: -0.40 ms). The start bit of
the first response byte must start within 15 ms after the stop bit of the last byte of the
command (t
olerance: +0.40 ms).
• After a sensor transmits the last character of a response, it must relinquish control of
the data line within 7.5 ms (tolerance: +0.40 ms).
• No more than 1.66 ms of marking are allowed between the end of the stop bit and the
start bit (for example between characters) on any characters in the command or the
response (no tolerance.) This permits a response to an M command to be sent within a
380 ms window.
• Sensors must return to a low-power standby mode after receiving an invalid address or
after detecting a marking state on the data line for 100 ms (tolerance: +0.40 ms).
• When a recorder addresses a dierent sensor, or if the data line has been in the
marking sta
te for more than 87 ms, the next command must be preceded by a break.
The low-power standby mode, in addition to being a low-power consumption state, is a
protocol state and it takes a moment to leave that state.
WXT530 Series User Guide M211840EN-D
178
sales@streamlinemeasurement.co.uk
www.streamlinemeasurement.co.uk
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