National Instruments NI-CAN, Руководство пользователя

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Chapter 2 Developing Your Application
NI-CAN User Manual 2-10 ni.com
Checking Status of Function Calls
Each NI-CAN function returns a value that indicates the status of the
function call. Your application should check this status after each NI-CAN
function call. The following sections describe the NI-CAN status, and how
you can check it in your application.
NI-CAN Status Format
To provide the maximum amount of information, the status returned by
NI-CAN functions is encoded as a signed 32-bit integer. The format of this
integer is shown in Figure 2-2.
Figure 2-2. Status Format
Error and Warning Indicators (Severity)
The error and warning bits ensure that all NI-CAN errors generate a
negative status, and all NI-CAN warnings generate a positive status. The
error bit is set when a function does not perform the expected behavior,
resulting in a negative status. The warning bit is set when the function
performed as expected, but a condition has arisen which may require your
attention. If no error or warning occurs, the entire status is set to zero to
indicate success. Table 2-1 summarizes the behavior of NI-CAN status.
Code
The code bits indicate the primary status code used for warning or errors.
Table 2-1. Determining Severity of Status
Status Result
Negative Error. Function did not perform expected behavior.
Zero Success. Function completed successfully.
Positive Warning. Function performed as expected, but a
condition arose that may require your attention.
31 30 29–16 15–0
Error Warning Qualifier Code