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Chapter 4, Status Reporting
Status Reporting
Status Register Programming Considerations
When performing certain tasks, such as making a call, program flow can be
controlled by the status register group bits. Generally, there are two approaches to
using status register group bits, Polling, and Service Requests. The choice of
which technique to use, polling or service request, will depend upon the needs of
the particular application.
Advantages/Disadvantages of Polling
Polling has the advantage that the control program can react quicker to the change
in state since it (the control program) does not have to execute the code necessary
to determine what condition caused the service request line to be asserted.
Polling has the disadvantage that, if improperly implemented, it can prevent the
Call Processing Subsystem from properly interfacing with the mobile station.
The Test Set has a multi-tasking architecture wherein multiple processes execute
on a priority driven and an event driven basis. One of the highest priority
processes is the process that services the GPIB.
If a control program constantly polls the status registers to determine when a
particular state is true, that state may never go to the true state because the Test Set
is constantly being interrupted by the GPIB service process.
Therefore, care must be exercised when using the polling technique to allow
enough time between polls for processes to execute within the Test Set.
Some computer systems and/or programming languages may not support the
service request feature of the GPIB and consequently polling would be the only
technique available to the programmer. When using a polling technique be sure to
include a delay in the polling loop. Refer to
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in the following example.
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