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16. Annex: RS232 Protocol
a) General Information
Command format
All commands to the transponder reader must be sent in the following format:
<STX><ADR><COMMAND><SUBCOMMAND><INDEX><DATA><CRC><EOT>
<STX>
ASCII Code 2
<EOT>
ASCII Code 4
<INDEX> 2 byte (4 ASCII characters)
Answer format
Answers from the transponder reader may have the following format:
Answer to successful command:
<STX><ADR><COMMAND><SUBCOMMAND><ACK><CRC><EOT>
Answer to defective command
<STX><ADR><COMMAND><SUBCOMMAND><ACK><CRC><EOT>
Answer to command with wrong format
<STX><ADR><NAK><CRC><EOT>
Answer to data query command
<STX><ADR><COMMAND><SUBCOMMAND><DATA><CRC><EOT>
Calculate useful ASCII codes and checksum:
<ACK>
ASCII-Code 6: Acknowledge
<NAC>
ASCII-Code 15: Not Acknowledge
All hexadecimal-encoded numbers are only recognised and output with capital
letters (0F and not 0f).
The checksum (<CRC>) is formed as crossfoot of the submitted ASCII characters
without <STX> and <EOT> and in turn sent as ASCII characters.
Start of Text
End of Transmission
for position indication of data
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