Omega Engineering OMB-NETSCAN 1500 User Manual Download

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Appendix A

API Command Reference

NetScan User’s Manual

A-3

Fixed Formats

Any Query (

)command or Status (

) command returns a fixed format. For instance, any option that can range

up to 65,535 always returns five digits, so zero would be returned as

00000

. In the following command

descriptions, leading zeros are included. They are not, however, required when entering the command.

Conflict Errors

Some combinations of commands and parameters can be sent to the unit

that are out of range for a particular

configuration or inconsistent with other commands. For instance, specifying a Scan Interval (

) command to

less time than the unit can acquire scans results in a conflict error:

PRINT#1,"C1-992,I00:00:00.0,00:00:00.0X"

A conflict error lights the ERROR indicator LED on the scanning unit and returns an

when queried with the

Error Query (

) command. Some conflict errors result in a default value for a conflicted command. For

instance, in the example above, the scan interval defaults to the fastest possible scan interval for the number of
defined channels.

Command Interpretation

As commands are received by the unit, they are interpreted in the order in which they are received. Some
commands are immediate, which means they immediately take effect. Other commands are deferred and have
no effect on device operation until the Execute (

) command is interpreted.

Immediate & Deferred Commands

The immediate and deferred commands applicable to NetScan are listed in a table on the following page.

An example of an immediate command is Set Digital Outputs (

), which immediately chooses the digital

output line which is being referred to.

An example of a deferred command is Set Data Format (

), which determines the input and output format used

for channel data when

is interpreted. As deferred commands are interpreted, their desired effects are recorded

in internal temporary registers. As additional deferred commands are interpreted, their effects are added to these
registers, possibly overwriting earlier effects. Finally, when

is interpreted, the temporary registers are

examined in the execution order described below. If two deferred commands that do not affect the same
function are received before the Execute (

)command, they take effect in the execution order described below.

If a deferred command is sent multiple times within a command line, the last occurrence of the command will
take precedence. Note that a command line is terminated by the

. For example, if

F1,1 F1,3X

is sent, the

data output format will be as specified by the

F1,3X

command. The

F1,1

command is overridden and never

takes effect.

If an error is detected during command processing, commands are ignored up through and including the next
execute command. Thus, any immediate commands after the error, (and all deferred commands) are ignored.
For example, the command line

T1,1,0,0O216,0,25, 255AAT3,7 K20 X

containing the error

only

executes the

, because it is an immediate command that occurred before the error. The deferred commands

T1,1,0,0

and

T3,7,0,0

and the immediate command

K20

after the error have no effect.

Deferred commands help reduce the effects of errors and improve synchronization of command execution. The
primary advantage of deferred commands is that they are executed as a group, either all or none. If any errors
occur, deferred commands have no effect and the device is left in a consistent state instead of a partially
modified, inconsistent state.