INFICON SQC-310 Thin Film Deposition Controller - Manual (Page 70)

Chapter 5 Communications
5-2
 The CRC is shifted right one bit position.
 If a character’s least significant bit is a 0 then the CRC is exclusive OR’d with 2001h
 Steps b and c are repeated for each of the 8 bits in the character.
The CRC contains 14 significant bits. This is split into two characters of 7 bits each,
and then a decimal 34 is added to offset the character outside the range of the Sync
Character.
Once a command is received by the SQC-300, it responds with a Response Status
character as shown below:
Response Status Meaning
A Command understood, normal response
B Command understood, but instrument reset
C Invalid command
D Problem with data in command
E Instrument in wrong mode for this command
If the response status is “A”, the requested data follows the status character.
An example application, MessageGen is supplied on the Utility CD to assist in
developing your communications program. MessageGen allows you to type in the base
command (without sync, length, and CRC characters) and view the complete command
sent to the SQC-300, and the complete response.
In this example, the complete Get Model command (“@”) is 5 characters long: A sync
character (!), the length (34 + 1 = “#”), the command (“@”), and the two CRC characters
(“O7”). The two values shown in parenthesis after the sync characters are the ASCII
value of the CRC characters. They are informational only, and were not actually sent to
the instrument.
The format of the response is identical, except that the third character (after sync and
length characters) is the Response Status character (“A”).