INFICON SQM-242 Thin Film Deposition Controller Card Software Operating Manual - Manual (Page 78)

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SQS-242 Operating Manual
5.6.2.3 Example Response: Set Process Update Failed
@UP;<NAK>;<ERR>;??<CR>
Where:
01
Illegal Command
02 Illegal Parameter
03 Illegal Format
04 Checksum Error
05 Request Denied
06 Unknown Error
5.7 Checksum Calculation
The sample code below calculates the FCS checksum of a string of characters.
In the code, Message is a string that has been stripped of terminator and checksum
characters before being passed to this routine.
' XOR ASCII codes
For i = 1 To Len(Message)
FCS = Asc(Mid$(Message, i, 1)) Xor FCS
Next i
' Convert FCS to two character hex string
If Len(Hex$(FCS)) = 1 Then
CalcChkSum = "0" & Hex$(FCS)
Else
CalcChkSum = Hex$(FCS)
NOTE: While checksums “may” be useful for RS-232 communications, they are
not needed for Ethernet or ActiveX. If you don’t want to use a checksum,
replace the checksum in each command with “00” (two ASCII zero (Hex
30) characters). The program response will contain two checksum
characters, which you can just ignore.