Geysitech (Bayern-Hessen) Protocol
Block Checksum <BCC>
Thermo Fisher Scientific Model 49i Primary Standard Instruction Manual D-3
If a command is terminated with <ETX> then additional two characters
<BCC> is attached after <ETX>, this is the block checksum.
Block Checksum
<BCC>
The block checksum is calculated beginning with a seed value of 00000000,
binary (0x00), and bitwise exclusive ORing with each of the characters of
the command string (or response) including the framing characters <STX>
and <ETX>. The checksum works as an error check. The command
terminator determines the presence or absence of <BCC>.
If a command is terminated by <ETX> then the next two characters are the
checksum, if the command is terminated with <CR> no checksum is
attached
The block checksum is represented by two characters, which represent a 2
digit hex number (1byte). (e.g. 1 byte 0xAB hex checksum will be
represented by the two characters ‘A’ & ‘B’)
The checksum is referred to as <BCC> throughout this document.
Geysitech Commands The following commands are supported by the Geysitech protocol:
• Instrument Control Command (ST)
• Data Sampling/Data Query Command (DA)
Instrument Control
Command (ST)
There are three control commands supported by the Geysitech protocol.
This <control command> is a single letter, which triggers an action in the
instrument. These commands are active only when service mode is inactive
and the zero/span option is present.
Command ‘N’ switches the instrument gas mode to Zero.
For the 49i PS, command ‘K’ switches the instrument gas mode to
Level 1.
For the 49i, command ‘K’ is not used unless the Sample/Cal option is
present. When the Sample/Cal option is present:
• If the ozonator is present, command ‘K’ switches the instrument gas
mode to Level 1.
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