Xylem H-3311 - Manual (Page 18)

16
SDI-12 COMMAND &
RESPONSE PROTOCOL
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
Initiate Verify Command
example of an “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
The “Send Identification” command responds with sensor vendor, model, and version data. Any
measurement data in the sensor’s buffer is not disturbed.
Send Identification Command