H-424ms – Xylem H-424MS V1.0 User Manual
Page 20
2-4 SDI-12 Command and Response Protocol
H-424MS
Example of a H-424MS "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
2.4 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