HERMOS LFM 4x - ASCI-I1 Communication Protocol; Structure of the Communication Protocol; Packet Content; Packet Header

Customer manual
LFM 4x Reader
RFID
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HERMOS AG
Gartenstraße 19 • 95490 Mistelgau
Phone: +49 9279 991 - 0
E-mail: rfid@hermos.com
LFM 4x Reader Rev1.4
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10. ASCI-I1 Communication protocol
10.1 Structure of the communication protocol
The communication is carried out via ASCII packets.
After each command to the reading device, a specific reply is transmitted. We recommend
waiting for this reply before transmitting a new command.
10.2 Packet content
Each message packet consists of a packet header (header = 3 characters), the message
data (2 or more characters) and the packet end.
Packet header
Message data
Packet end
Packet header
The packet header contains a start character and the message length. The message length
consists of 2 hexadecimal bytes and defines the number of characters in a message.
Packet header
Start character
Length 1 (high byte)
Length 2 (low byte)
Start Start character (ASCII character „S“)
Length 1 High byte of the message length (ASCII character „0“-“F“)
Length 2 Low byte of the message length (ASCII character „0“-“F“)
Advanced ASCII-format:
The advanced ASCII format is defined for ASCII messages whose message length
exceeds 255 characters. The packet header contains two start characters and the
message length. The message length consists of 4 hexadecimal bytes and defines the
number of characters in a message.
Packet header
Start 1
Start 2
Length 1
Length 2
Length 3
Length 4
Start 1 First start character (ASCII-character „S“)
Start 2 Second start character (ASCII-character „X“ = advanced ASCII protocol)
Length 1 High byte of the message length (ASCII-character „0“-„F“)