Xylem H-335 - Manual (Page 22)

2-6 SDI-12 Command and Response Protocol H-335
Example of a H-335 "aV!" command:
Command Response Time Values Description
"aV!" "a0013"
1 sec 3 Return fixed data and diagnostic
data for testing purposes.
Subsequent Command Response
"aD0" a+123.456+78.9+y
Key Description Units
+123.456 Fixed test data
+78.9 Fixed test data
y ROM checksum test 0 = Failed, 1 = Passed
2.5 Continuous Measurements
This is a new command for the Version 1.2 SDI-12 Specification. Sensors that are able to continuously monitor
the phenomena to be measured, such as a cable position, do not require a start measurement command. They
can be read directly with the R commands (R0!...R9!). The R commands work exactly like the D (D0!...D9!)
commands. The only difference is that the R commands do not need to be preceded with an M command. The
H-335
DOES NOT supports the aR0! continuous measurement commands.
2.6 Initiate Verify Command
The Verify Command causes a verify sequence to be performed. The result of this command is similar to the
"aM!" command except that the values generated are fixed test data and the results of diagnostic checksum
tests. The data generated in response to this command is placed in the sensor's buffer for subsequent collection
using "D" commands. The data will be retained in the sensor until another “M”, “C” or “V” command is
executed.
Command Response Description
"aV!" "atttn" Initiate verify sequence
Where:
a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
V is an upper-case ASCII character.
ttt is a three digit integer (000-999) specifying the maximum time, in seconds, the
sensor will take to complete the command and have data available in its buffer.
n is a single digit integer (0-9) specifying the number of values that will be placed
in the data buffer. If "n" is zero (0), no data will be available using
subsequent "D" commands.