EUCHNER CIS3(A) - Manual (Page 9)

EUCHNER Identsystem CIS3
071652-01-8/99 Subject to technical modifications page 9 / 23
4.2.3 Summary of the most important points
• DLE doubling:
In order for the control to be able to distinguish between control character DLE and any
randomly occurring DLE as user information character, a further DLE must be sent in
the case of a DLE as user information character. This means that if a byte with ASCII
value DLE ( 10
HEX
) occurs within the telegram core, this character must be transmitted
again so that it is not interpreted by the distant station as a control character for
connection cleardown.
• Block check character (BCC):
A block check character is sent at the end of each data block for data integrity. The block
check character BCC is the even longitudinal parity (EXORing of all data Bytes) of a
transmitted or received block. Generation starts with the first user data Byte (first Byte
of the telegram) after connection set-up and ends after characters DLE and ETX on
connection cleardown.
• Retry attempts in the case of errors:
If an error occurs for any reason during data transfer, a total of 6 attempts are made to
transfer the data correctly.
Please refer to the program example in the Annex of this Manual for further details.