8-22 HP IBASIC Supplement
Interfacing with External Devices
Interfacing with an External Controller
Synchronizing IBASIC with an External
Controller
Using OUTPUT and ENTER Statements
Commands sent to the analyzer with OUTPUT and ENTER statements
from IBASIC and from the external controller at the same time must be
synchronized by the programmer. These commands cannot be allowed to
overlap. Overlapped commands sent from the external controller and
IBASIC will result in unpredictable behavior or deadlocks.
For example:
If the external controller executes:
OUTPUT 716;”<command>”
and IBASIC simultaneously executes:
OUTPUT 800;”<command>”
the results are unpredictable.
To avoid overlapped commands, you must ensure that only the controller
is allowed to send commands or only IBASIC is allowed to send
commands at any one time. One possible method to avoid overlap is
described below. For this method, when the respective controller is done
sending commands, the other controller is informed. The alternate
controller may then begin sending commands. After each set of
commands is completed, the alternate controller is informed and given a
signal to send commands to the analyzer. See example program TRICTRL
in the Example Programs Guide.
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