Chapter 5 communications, Chapter 5 - communication s – INFICON SQC-310 Thin Film Deposition Controller User Manual
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Chapter 5
Communications
5-1
Chapter 5 - Communication s
5.0 Introduction
The SQC-300 series communicates with a host computer through three possible
protocols:
1. RS-232: 19200 baud, 8 data bits, and no parity
2. USB: PID 8292
3. Ethernet (option): Port 2101, Address 192.168.1.200.
5.1 SQC300 COMM.EX E
SQC300 Comm .exe is found on the Utility and Demo disk supplied with your SQC-300.
A current version may be also be downloaded from 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-300 and save
them to disk. Contact Sigma Instruments if you would like the vb source code.
5.2 Communications P rotocol
The SQC-300 communicates with a host computer via a serial ASCII protocol at 19200
baud, 8 data bits, and no parity. The SQC-300 only responds to commands received. It
never initiates communications.
The command protocol sent to the instrument is:
sync character> <length character> <1 to n data characters> <CRC1><CRC2>
The sync character is always an exclamation point ‘!’. Following the sync character is
the length character. This is the number of characters in the packet (not counting the
sync, length, and CRC characters). The length character has a decimal 34 added to it
so there cannot accidentally be a sync character (!) embedded in the packet.
Following the length character are the command and data characters as detailed later in
this section. After the data come two CRC characters.
Note: If you do not wish to use CRC checking in your application, just send two Null
charcaters (CHR$0) for the CRC. The SQC-300 will ignore the CRC. The SQC-300 will
still return a CRC in its response, but you can ignore it.
The CRC is computed using the following algorithm:
The CRC is initialized to 3FFF hex.
Each character in the message is examined, bit by bit, and added to the CRC in the
following manner:
The character is exclusive OR’d with the CRC.