Registers, Data Formats, & Queries Appendix D
D-10 NetScan User’s Manual
The NetScan provides many ways to query the unit for specific information. Most commands have a
corresponding query command which responds with the configuration or mode of a previously executed
command. In addition, the U Status commands can be used at any time (without interfering with normal
operation) to return information about the various NetScan conditions.
Query (?) Commands
Most commands have a corresponding query command formed by appending a question mark (?) to the
command letter. Query commands place their responses into the output queue until the controller retrieves
them. They respond with the present configuration or mode of a previously executed command. When
appropriate, the response from a query command is in the form of a command string which, if it were executed,
would put the unit into the configuration it was in when the query was executed. For instance, the response to
the User Terminator query command V?X is in the form:
Vuser (where 0< user <255)
This response is in the form of the User Terminator (V) command and, if it is sent to the NetScan, it would set
the User Terminator to the same value that it had when the query was issued. Query responses are always fixed-
length strings in a pre-defined format.
Any number of query commands can be combined into one string to create a specialized status command that
responds with only the information of interest for a given application. Query commands are immediate; in other
words, their command responses are generated as soon as they are interpreted and before any other commands,
including the Execute (X) command. For example:
PRINT#1,"V1 X V? X" ‘ Get the response of current User Terminator
INPUT#1, A$ ‘ Retrieve response..
PRINT A$ ‘ Screen shows V1
PRINT#1,"V0 X V? X" ‘ Change User Terminator and get response.
INPUT#1, A$ ‘ Retrieve response.
PRINT A$ ‘ Screen shows V0
PRINT#1,"V4 V? X" ‘ Change User Terminator and Get response - No intermediate X command.
INPUT#1, A$ ‘ Retrieve response...
PRINT A$ ‘ Screen shows V0 User Terminator. Response is still V0 because V? was
executed before V4 since V? is an immediate and V4 is a deferred
command.
PRINT#1,"V? X" ‘ Get User Terminator response
INPUT#1, A$ ‘ Retrieve response..
PRINT A$ ‘ Screen shows new User Terminator — V4.
Even though query commands generate their response as soon as they are interpreted, they must still be followed
by an Execute (X) command for proper termination. For more information on command execution, refer to the
X command in Appendix A.
U Status Commands
Status commands are used to return information about various conditions of the NetScan. The status of the
NetScan may be read at any time without interfering with normal operation. Any error conditions, except
Calibration Errors, are cleared after the status string is read by the controller. The Calibration Errors are cleared
when the unit is calibrated.
Status strings are returned when the NetScan is next addressed to Talk. The terminators used and the use of the
End or Identify (EOI) line can be changed with the Q commands.
If the NetScan is configured to trigger on Talk, requesting a status report (U command) will not cause the
NetScan to trigger.
The following table outlines the information available through the U commands. See the Command Reference
section for details and examples.