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ZBasic System Library

ZBasic Microcontrollers

Note, particularly, the line immediately before the call to ShiftOut(). After the semaphore is acquired

Regsister.Timer1Busy will be True. Unless it is set to False, the call to ShiftOut() will fail

because that subroutine will think that the timer is in use.

Caution: setting the busy flag for a timer to True and never setting it back to False will prevent the

proper functioning of all System Library routines that require that timer.

I/O Timer Prescaler Values

Some of the System Library routines that use the I/O Timer allow you to modify the frequency used to

clock the timer while others use a fixed frequency determined by the requirements of the routine. The

routines that do allow frequency modification are divided into two groups, one controlled by the value of

Register.TimerSpeed1 and the other controlled by the value of Register.TimerSpeed2. The

table below shows the System Library routines that use a timer and, where applicable, the timer speed

variable that controls the timer frequency.

System Library Routines Using TimerSpeed Values

TimerSpeed Value

CountTransitions()

InputCaptureEx()

OutputCapture()

OutputCaptureEx()

The timer frequency is scaled in some cases. See below.

The timer is used only for software based channels.

The table below shows the correspondence between the allowable values for the TimerSpeed registers

and the resulting clock frequency applied to the I/O Timer in terms of the CPU frequency. The divisor

specified is applied to the CPU clock frequency to yield the I/O Timer clock frequency. For compatibility