Start character "/" = 2F hexadecimal.

End character "!" = 21 hexadecimal.

Transmission request command "?" = 3F hexadecimal.

Completion character appears always double.
"CR"  carriage return = 0D hexadecimal
"LF"  line feed          = 0A hexadecimal

The frame start character  "STX" = 02 hexadecimal indicates the beginning of the calculation of the BCC. 

The frame end character "ETX" = 03 hexadecimal indicates the end of the calculation of the BCC. The ETX is included in the calculation. 

The "Block check character" is the calculated length parity over the characters of the data message beginning immediately after the STX up to the included ETX .

The Device address is manufacturer-specific and may consist of maximum 32 characters. This field is optional. The characters can be digits "0...9", upper case letters and lower case letters "aA...zZ" and a space. 

The Manufacturers identification consists of three upper case letters except the third letter, it can also be transmitted as a lower case letter. If the third letter is a lower case letter, that means that the tariff device has a minimum reaction time of 20ms instead of 200ms. If the device transmits only upper case letters it does not preclude that it does not support 20ms. 
( see <FLAG : Registered Manufacturers Identification Characters> )

The Baud rate identification is used for the baud rate changeover. The "request message", the "identification" and the "acknowledgement/option" are transmitted with an initial rate of 300 Bd ( not valid for protocol mode D ). The baud rate identification in the message is determined by the used protocol mode. 

Protocol mode A :
No baud rate changeover is provided for this mode. Each character is allowed, excepted are the characters "/", "!" and the character may not be specified as baud rate for protocol mode B or C. 

Protocol mode B with baud rate changeover :
In this mode the "acknowledgement/option" is not used.
A -   600 Bd
B -  1200 Bd
C -  2400 Bd
D -  4800 Bd
E -  9600 Bd
F - 19200 Bd
G, H and I are reserved.

Protocol mode C and E with baud rate changeover :
The "acknowledgement/option" is only used in this modes. 
0 -   300 Bd
1 -   600 Bd
2 -  1200 Bd
3 -  2400 Bd
4 -  4800 Bd
5 -  9600 Bd
6 - 19200 Bd
7, 8 and 9 are reseved.

Protocol mode D :
No baud rate changeover is provided for this mode. Data transmission is determined on 2400 Bd. The baud rate identification is always 3.

The identification is manufacturer-specific and may consist of maximum 16 characters. Each character is allowed, excepted are the characters "/", "!". The character "\" is only allowed as ESC character and only in connection with the two optional fields "sequence delimiter" and "mode identification.

The sequence delimiter "\" = 5C hexadec is always followed by the mode identification character and occurs only with this character. This field is optional and part of the 16 characters long identification.

Die Mode identification character defines the protocol mode E. The field is optional and part of the 16 characters long identification.

0 and 1 are reserved
2 - binary mode ( HDLC )
3 up to 9 are reserved

The protocol control character is used in protocol mode C and E. 

0 - normal protocol procedure
1 - secondary protocol procedure
2 - HDLC protocol procedure
3 up to 9 are reserved

The mode control character is used in protocol mode C and E.

0 - read data
1 - programming end
2 - binary mode ( HDLC )
3 up to 5 and A up to Z is reserved for later use. 
6 up to 9 for manufacturer-specific use

The address i.e identification may have a maximum size of 16 characters. Each character is allowed, excepted the characters "(", ")", "/" and "!".

Front boundary character " ( " = 28 hexadecimal.

The value may have a maximum size of  32 characters. Each character is allowed, excepted are the characters "(", " * ", ")", "/" and "!". The dot should be used instead of a comma for values with decimal hyphen. The hyphen is counted in the number of characters. 

Separator character " * " = 2A hexadecimal. The character can be left out if no unit exists. 

The unit may have a maximum size of 16 characters. Each character is allowed, excepted the characters "(", ")", "/" and "!". 

Rear boundary character " ) " = 29 hexadecimal.

The Frame start character "STX" = 02 hexadecimal, indicates the beginning of the calculation of the BCC.

The Frame end character "ETX" = 03 hexadecimal, indicates the end of the calculation of the BCC. The ETX is included in the calculation. 

The "Start of header" character "SOH" = 01 hexadecimal, indicates the beginning of the calculation of the BCC.

The "End of text" character "EOT" = 04 hexadecimal.

The "Block check character" is the calculated length parity over the characters of the data message beginning immediately after the STX up to the included ETX .

Command message identifier :

P - Password command
W -Write command 
R - Read command 
E - Execute command
B - Exit command ( break ) 
Other characters are reserved for later use.

The Command type identifier defines the variant of the command. 

Password command :
0 - data is operand for secure algorithm
1 - data is operand for comparison with internally held password
2 - data is result of secure algorithm ( manufacturer specific )
3 up to 9 is reserved for later use.

Write command :
0 - reserved for later use.
1 - write ASCII-coded data
2 - formatted communication coding method write ( optional )
3 - write ASCII-coded data with partial block ( optional )
4 - formatted communication coding method write with partial block (optional)
5 - write/ delete ASCII-coded data ( Load profil, Logbook, .. )
6 up to 9 is reserved for later use..

Read command :
0 - reserved for future use
1 - read ASCII coded data
2 - formatted communication coding method read ( optional )
3 - read ASCII coded data with partial block ( optional )
4 -  formatted communication coding method read with partial block (optional)
5 - read ASCII coded data ( Load profil, Logbook, .. )
6 - read ASCII coded data with partial block ( Load profil, Logbook, .. )
7 up to 9 is reserved for later use

Execute command :
0 - 1 reserved for later use
2 - Formatted communication coding method execute ( optional )
3 up to 9 is reserved for later use 

Break command :
0 - complete sign off
1 - complete sign off for battery operated devices using the fast wake up
     method
2 up to 9 is reserved for later use 

The address ie identification may have a maximum size of 16 characters. Each character is allowed, excepted the characters "(", ")", "/" and "!".

Front boundary character " ( " = 28 hexadecimal.

The value may have a maximum size of 32 characters. In protocol mode C however  the value can have a maximum size of 128 characters. Each character is allowed, excepted are the characters "(", " * ", ")", "/" und "!". The dot should be used instead of a comma for values with decimal hyphen. The hyphen is counted in the number of characters.

Separator character " * " = 2A hexadecimal. The character can be left out if no unit exists.

The unit may have a maximum size of 16 characters. Each character is allowed, excepted the characters "(", ")", "/" and "!". 

Rear boundary character " ) " = 29 hexadecimal.