INFICON SQC-222 Thin Film Deposition Controller - Manual (Page 71)

Chapter 5 Communications
5-1
5.0 Introduction
This section covers external control of the SQC-222 by RS-232 commands.
5.1 SQC222 COMM.EXE
SQC222 Comm .exe is found on the Utility and Demo disk supplied with your SQC-222.
A more current version may be available on
www.sig-inst.com .
The program provides instrument control and data graphing. It also allows you to set
process, layer, film, and material parameters, download them to the SQC-222 and save
them to disk. This program is written in Visual Basic. Contact Sigma Instruments if you
would like the source code for this program.
5.2 Communications Protocol
The SQC-222 communicates with a host computer via an ASCII based protocol. The
instrument defaults to 19200 baud, 8 data bits, and no parity. The basic protocol is:
<sync character> <length character> <1 to n data characters> <CRC1><CRC2>
Once a valid command has been transmitted to the SQC-222, a response is returned.
The structure of the packet is identical in both the command and response. In the
response, the first character is a Response Status. These are summarized in the
following table.
Response Letter 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
The sync character is an exclamation point ‘!’. Anytime this character is received, the
communications buffer of the SQC-222 is reset for a new packet.
Following the sync character is the length character. This is the number of characters in
the packet starting with the length and counting the 2 CRC characters. This character
has a decimal 34 added to it so there cannot accidentally be a sync character
embedded in the packet.