INFICON SQC-310 Thin Film Deposition Controller User Manual
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SQC-310 Operating Manual
The CRC is computed using the following algorithm:
1
The CRC is initialized to 3FFF hex.
2
Each character in the message is examined, bit by bit, and added to the CRC
in the following manner:
2a
The character is exclusive OR’d with the CRC.
2b
The CRC is shifted right one bit position.
2c
If bit position 0 has a value of 1 before each shift, the CRC is exclusive OR’d
with 2001 hex. This is done a total of 8 times per message character.
3
Step 2 is repeated for each character in the message (excluding the sync and
length characters).
4
Mask the contents of the CRC by logical AND with 3FFF hex.
5
The CRC contains 14 significant bits. This is split into two pieces of 7 bits each.
A decimal 34 (22 hex) is added to each CRC in order to avoid there being an
embedded sync character.
5a
Extract bits 0 - 6 of the CRC and add a decimal 34 (22 hex). This is CRC1.
5b
Extract bits 7 - 13 of the CRC and add a decimal 34 (22 hex). This is CRC2.
NOTE: Sync characters are not included in the CRC calculation.
Code examples for calculating the CRC can be found in
.
Once a command is received by the SQC-310, it responds with a Response Status
character as shown in
.
If the response status is “A”, the requested data follows the status character.
Table 5-1 Response Status Characters
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