Var: modify or query system variables – Sierra Video Tahoe Series 16 User Manual
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Sierra Video Systems
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Every “G” command must be terminated with a tilde (‘~’) character. This allows a
command parser to ignore any received “G” command that has a command_name that it
doesn’t know about.
The “G” commands available for any given router may vary, depending on the router
model. The “G SUPPORTED” command allows controllers to find out whether particular
“G” commands are supported by a given router or not.
A router may be sent “G” commands that it doesn’t understand. It will simply ignore them
and generate an ERROR response.
VAR: Modify or query system variables
Action
From Syntax
Modify
Host G
VAR,
Query
Host G VAR,
Query Response
Router (same as Modify)
Modify is Protected:
Yes
Report Changes:
No
The “G VAR“ command is used to change or query system variables that control specific
features of the router. The variable being affected is specified using its name, and only
one variable at a time can be targeted by this command. The features being controlled
are typically system options that allow the user to control special hardware or software
enhancements to the router code.
The Modify command has two or more arguments, the name of the variable to be
changed and the new value of that variable. Most variables have only a single value
associated with them, but it is possible for a variable to be multi-valued, in which case the
number of
The Query command has the variable name whose value is to be queried as the only
argument.
The Query Response command has the same argument structure as the Modify
command.
Each different router may support different variables. The supported variables may grow
over time, as enhancements are added to this protocol, so command parsers should
generally ignore unknown variable names. The routers themselves will ignore any
command that is received with an unknown variable name or an invalid variable value.
Use the “G VARQRY” command to find out which variables a particular router actually
supports. Refer to documentation for each router for a description of the variables.
A variable value is typically an unsigned decimal number, but may also be a signed
decimal number. The “G VARQRY” command can be used to determine the allowed
range of values.
For example, to query for the value of a variable named “VI_DELAY”:
** G VAR,VI_DELAY~ !!
The response command might be:
** G VAR,VI_DELAY,4~ !!
To set the “HD_SLAVE” variable to 1:
** G VAR,HD_SLAVE,1~ !!