2 – 4
Remote Operation
2.3
Commands
This section provides syntax and operational descriptions for remote
commands.
2.3.1
Command syntax
Communication with the SR475 and SR476 uses ASCII characters.
All commands are one character long and are case sensitive.
Commands are executed when the command character is received
without waiting for additional data or confirmation. No command
terminator should be used. While this style of execution is referred to
as “immediate,” remote commands are not executed with precision
timing (
§
2.2.2).
The command bu
ff
er is limited to 16 bytes. If the bu
ff
er overflows,
a bit will be set in the error word, and the last command will be
discarded.
Query commands, which are commands that request a return of data,
will return exactly seven bytes of data, of which the last byte is
LF
(ASCII 10). Numbers are formatted as signed integers, where the
leading character is ‘-’ for negative numbers or ‘ ’ (ASCII 32) for
positive numbers.
Aside from communication errors, commands may fail due to either
syntax or execution errors. Not all such failures will generate a fault.
As an example, if the shutter is initially open, a command to open
the shutter will simply be ignored.
All commands (ASCII characters) that are not in the command list are
reserved for future use and
/
or factory use. Commands that are not
in the list may produce unpredictable results and should be avoided.
Errors and changes in shutter status can be detected by requesting
the status word and error word, with commands
W
and
Z
.
2.3.1.1 Examples
Commands may be given with a simple example illustrating their
usage. In these examples, commands sent by the host computer
to the SR475 or SR476 are set as
straight teletype font
, while
responses received the host computer from the shutter head are set
as
slanted teletype font
.
These examples are not exhaustive, but are intended to provide a
convenient starting point for user programming.
SR475 and SR476 Laser Shutters
