INFICON Cygnus Thin Film Deposition Controller - Manual (Page 108)

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Cygnus Operating Manual
5.3 Message Protocols
The message protocol serves as a structure for the contained command or
response information. It also can provide a level of acknowledgment between the
host and server and a mechanism for verifying the information content.
5.3.1 INFICON Cygnus Message Formats
The same message format is used for the serial port and for the IEEE-488 port. All
messages are comprised of byte serial information. The byte values represent
command or response characters, control characters, or numeric values.
Mnemonics will be used to describe portions of each message format.
NOTE: These mnemonics are not part of the message stream; they are used to
represent specific ASCII codes, characters or numeric values that
comprise the message stream.
5.3.2 Basic Protocol
Key:
<> . . . . . . . . . . . . . . . . . . . . . . . . Enclosed element further defined below (or
above, if repeated use)
() . . . . . . . . . . . . . . . . . . . . . . . . . Optional Element
I . . . . . . . . . . . . . . . . . . . . . . . . . Or
x...x. . . . . . . . . . . . . . . . . . . . . . . One or more of x included
5.3.2.1 Command Packet (Host to Instrument Message)
<length><message><checksum>
Length . . . . . . . . . . . . . . . . . . . . 2 bytes Low / High (not including checksum
or length bytes) Numeric value from 0 to
16,383 (two bytes) representing the number
of characters in the command. In order of
transmission, the low byte will precede the
high byte. For most commands, the number
for characters will be less than 256. In this
situation the low byte will contain the
character count while the high byte will have
zero value.
Message. . . . . . . . . . . . . . . . . . . <Command>(<Command>...<Command>)
Command = <Command Group>
(<Command Sub-group>) (<Command ID>)
(<Parameter>...<Parameter>)