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Continuous Timer
Ivan Cenov edited this page Feb 23, 2019
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This timer measures consecutive equal intervals and at the end of each of the intervals raises TimerTick flag. So it is capable to trigger periodic events in an embedded system.
| Macro | Description |
|---|---|
| DEFINE_CONTINUOUS_TIMER(tag,ttype) | Declare a continuous timer in .c file by declaring its variables. tag is the tag of the timer, and ttype is its type. |
| EXTERN_CONTINUOUS_TIMER(tag,ttype) | Define external definitions in .h file. tag is the tag of the timer, and ttype is its type. |
| Variable | Description |
|---|---|
| ContinuousTimerCounter(tag) | Counter of type ttype. Can be used as lvalue. Direct access to this variable is not recommended. |
| ContinuousTimerSetting(tag) | Period of the timer. Can be used as lvalue. It is used to load ContinuousTimerCounter(x) at the end of the current interval. |
| ContinuousTimerFlag(tag) | When true, this flag indicates active, working timer. When false the flag indicates a stopped timer. |
| ContinuousTimerTick(tag) | This flag, when true indicates that an interval with period of ContinuousTimerSetting(tag) has expired. When an application sees this flag risen, it should clear it by calling ClearContinuousTimerTick(tag) and eventually execute some periodic actions. |
| Macro | Description |
|---|---|
SetContinuousTimer(tag,per) |
This macro activates a timer with tag tag to measure intervals per. per must be an expression of the same type that was used in DEFINE and EXTERN macros. ContinuousTimerFlag(tag) is set to true, ContinuousTimerTick(tag) is set to false. ContinuousTimerSetting(tag) and ContinuousTimerCounter(tag) to per. The macro disables the interrupts at the beginning and enables them at the end. |
SetContinuousTimer(tag,per) |
This macro activates a timer with tag tag to measure intervals per. per must be an expression of the same type that was used in DEFINE and EXTERN macros. ContinuousTimerFlag(tag) is set to true, ContinuousTimerTick(tag) is set to false. ContinuousTimerSetting(tag) and ContinuousTimerCounter(tag) to per. The macro does not touch the interrupts and thus it is convenient to be used with previously disabled interrupts. |
StopContinuousTimerI(tag) |
This macro stops a timer with tag tag. It simply clears both ContinuousTimerFlag(tag) and ContinuousTimerTick(tag). The macro disables the interrupts at the beginning and enables them at the end of the macro execution. |
ResetContinuousTimer(tag) |
This macro stops a timer with tag tag. It simply clears both ContinuousTimerFlag(tag) and ContinuousTimerTick(tag). The macro does not touch the interrupts and thus it is convenient to be used with previously disabled interrupts. |
ClearContinuousTimer(tag) |
This macro clears all variables associated with a timer with tag tag. The macro does not touch the interrupts and thus it is convenient to be used with previously disabled interrupts. Note: Normally, this macro is not much useful. It exists for history purposes. |
SuspendContinuousTimer(tag) |
This macros suspends a timer with tag tag while keeping the values of the counter and the setting. |
ResumeContinuousTimer(tag) |
This macro resumes a timer that was previously suspended. |
TickContinuousTimer(tag) |
This macro decrements by one ContinuousTimerCounter(tag). If the counter becomes zero, the macro raises ContinuousTimerTick(tag) and sets ContinuousTimerCounter(tag) to ContinuousTimerSetting(tag). |