ZBasic System Library
112
ZBasic Microcontrollers
Type
Function returning Byte
Invocation
DisableInt()
Discussion
This routine disables interrupts, preventing any interrupt source from interrupting the current task. Most
commonly, this function is used to temporarily disable interrupts thereby allowing a sequence of
instructions to execute without interruption. Of course, interrupts should be disabled for the shortest
possible time in order to avoid missing important interrupts (e.g. real time clock interrupts). If interrupts
are disabled for longer than one period of the RTC fast tick (i.e. 1/F_RTC_FAST) you run the risk of
missing an RTC tick which will result in the RTC losing time.
The most common use for DisableInt() is to implement “atomic access” to variables. This should be done
for any variable that occupies multiple bytes of memory (e.g. Integer, Long, etc.) or for a read-modify-
write operation on any variable when there is a possibility that another task or interrupt handler might
attempt to access the same variable.
The value returned by DisableInt() should be passed to EnableInt(). Doing so will allow proper nesting of
DisableInt() and EnableInt() calls.
Note
The Atomic block construct (described in the ZBasic Language Reference Manual) is the preferred
method for implementing atomic access.
Example
Dim iflag as Byte
iflag = DisableInt()
' place code here that must not be interrupted
Call EnableInt(iflag)
See Also
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