Thermo Scientific 5028i Instruction Manual page 319

Block Checksum
Characters <BCC>
Gesytec Commands
Instrument Control
Command (ST)
Thermo Fisher Scientific
The Block Checksum Characters are 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.
The following commands are supported by the Gesytec protocol:
Instrument Control Command (ST)
l
Data Sampling/Data Query Command (DA)
l
There is one control command supported by the Gesytec 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' initiates a filter change.
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>
The <address> is optional, which means it can be left out completely.
The <address>, if present, must match the Instrument Address.
Additional space can be present after the <address>.
If the received command does not satisfy the above formats, or if the
<address> does not match the Instrument Address, the command is
ignored.
Gesytec (Bayern-Hessen) Protocol
Block Checksum Characters <BCC>
Model 5028i Instruction Manual D-3