General Ak Protocol Description; Handling Of Certain Conditions - TESTO CU-2 User Manual

FUNCT.CODE2
4. Byte
FUNCT.CODE3
5. Byte
FUNCT.CODE4
6. Byte
7. Byte
ERROR STATUS
8. Byte
n. Byte
7.3.3.

General AK Protocol Description

•
Every transfer always starts with 'STX', each 'STX' starts a new transfer
•
The 'don't care' byte can take any content, excluding control signs or signs reserved by
AK commands. Default value is 0 (30 hex)
•
Every function code always includes 4 bytes. A list of all codes can be found in the
following chapters.
•
The function code may not contain blanks.
•
If the command message contains no error, the response message contains the echo of
the function code and the error status number (0 to 9).
•
The echo will be four question marks (????), if the function code has an error or is
unknown, or the command telegram has not a minimum length of 10 bytes.
•
There are three groups of function codes:
S = Control commands
A = Read commands
E = Write commands
(S, A, E stands for the German words: 'Steuerbefehle', 'Abfragen', 'Einstellbefehle')
•
The particle measurement system is a measurement device and not a functional engine.
Therefore, the identification respectively the channel number is always K0.
•
Error status is '0' for an error free running of the system. The error status number will be
counted up from 1 to 9 with each change in the error status. The error status number will
be zero again after all errors are removed.
•
The data set is variable. Each data set will begin with a blank (20 h) . A blank is also used
to separate characters of data. The separation with <CR><LF> will only be done, if the
following complete data will have more than 60 digits.
•
The long and variable floating point or the E- format are allowed to display the digits of
numbers in the data set. You can find the used formats for all functional codes in the
following chapters. '+/-' may only be used for negative numbers. Digits without physical
meaning have to be removed.
•
Every transfer always stops with 'ETX'
7.3.4.

Handling of Certain Conditions

•
If transfer of a data value is not possible, e.g. a device in the system is missing or it
cannot send a signal, the data will be replaced by a '#'
•
The date is only valid with restrictions, e.g. temperature of CPC is not ready. Then data
will begin with '#'
•
If a control or adjusting command is sent while the measuring device is in 'Manual' mode,
resp. not set to 'Remote', then response data set = 'OF' (offline)
•
If the system is not able to send a response. The host computer has to realize the
missing response by 'time out'
BLANK
FIXED DATA
VARIABLE DATA
DATA
(length depending
on functional code)
ETX END
20
blank (space, 20 h)
0 when no error, 1...9,
+1 every error status change
data depending on functional
code, can also disappear
03
end byte
7 AK Host Operation
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