ZBasicSysLib - page 24 of 323

ZBasic System Library

ZX Microcontroller Family

also used for some specialized I/O functions as indicated in the table above.

On ATmega-based devices, the Serial timer is also used for 8-bit PWM generation. Consequently, use of

8-bit PWM and use of Com3 to Com6 are mutually exclusive.

For each timer, there exists a built-in variable that indicates when the timer is in use. For example,

Register.Timer0Busy and Register.TimerC1Busy are Boolean values that indicate when Timer0

(ATmega) and TimerC1 (ATxmega), respectively, are in use. Prior to using a timer, the system checks

the value of this variable to see if it is already being used. If it is not in use, the system sets the flag to

True and then proceeds to use the timer. When it is finished using the timer, the system sets the busy

flag to False. Your program may do the same by passing the Register variable as a parameter to the

Semaphore() function.

I/O Timer Pre-scaler Values

Some of the System Library routines that use a 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. See below.