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Block Checksum
Geysitech Commands
Instrument Control Command
Thermo Fisher Scientific
The block checksum is calculated beginning with a seed value of
00000000, binary (0x00), and bitwise exclusive ORing with each of the
<BCC>
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.
The following commands are supported by the Geysitech protocol:
Instrument Control Command (ST)
●
Data Sampling/Data Query Command (DA)
●
There are three control commands supported by the Geysitech protocol.
(ST)
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 mode.
Command 'K' switches the instrument gas mode to Span mode.
Command 'M' switches the instrument gas mode to Sample mode.
The following are the different acceptable formats of the ST command:
<STX>ST<address><control command><ETX><BCC>
OR
<STX>ST<address><control command><CR>
OR
<STX>ST<address><SP><control command><CR>
OR
<STX>ST<address><SP><control command><ETX><BCC>
Geysitech (Bayern-Hessen) Protocol
Block Checksum <BCC>
Model 42i Trace Level Instruction Manual
D-3
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