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7.2 Protocol structure
All the commands have the following structure:
STX, command in ASCII, CRC in ASCII, ETX
The following answers are possible:
A Record with the structure given above,
ACK
BEL
NAK
Except STX and ETX, the total content of the commands are composed in
ASCII characters.
This procedure has been chosen explicitly, as a large number of host Operating
Systems react with their own functions, when they see characters outside of 0x20
to 0x7F.
The CRC is applied only on the characters of the „command“, STX and ETX are
not
included.
The 4 nibbles of the CRC are transmitted in form of 4 ASCII characters. By
doing so, the CRC is in conformance with the ASCII standard as well.
Control Control Control Control
characters
characters characters
characters
Hex Hex Hex Hex
code
code code
code
Designation Designation Designation Designation Function Function Function Function
STX 0x02 Start Of Text Begin of a Records
ETX 0x03 End Of Text End of a Records
BEL 0x07 buzzer (bell) Signaling a specific condition, e.g..
if the interrogated memory site is
not occupied.
CR 0x0D Carriage Return End of string
ACK 0x06 Acknowledge The command has been executed
successfully
NAK 0x15 Negative Acknowledge The command was not recognized
and consequently has not been
executed (syntax error)