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I) V24/RS232/485-Interface - Basics
90003752(2) [AK-Commands] 11/01
AK
1 - 7
4. Specifications of data settings
4.1. Head telegram (Header)
The begin of each transfer is a "STX" in the first byte. Each "STX" will start a new transfer.
Previous transfers will be deleted, if they are not finished by "ETX". That means, only
completed telegrams may be interpreted and answered.
You can take any content for the "DON'T CARE" byte, excluding control signs or signs
reserved by the AK commands.
For the RS485 BUS operating an address byte will be used instead of the "DON'T CARE"
byte. The analyzers will only answer to this command if the bus address setup will concur
with this byte.
In the command telegram a function code will be sent to the system unit or the analyzer
with the four function bytes.
In the response telegram this function code will be sent back as an echo if the transfer is
successful. The echo will be four question marks (????), if
• the command telegram has not minimum the number of bytes of the head telegram, the
channel number in the data part and the end telegram (number of bytes = 10; using a
channel number with two digits = 11 bytes) or
• the function code has errors or is unknown.
The function code may not contain blanks.
There are three groups of function codes:
(1) Control commands
(2) Read commands
(3) Write commands