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ZBasic System Library
11
ZX Microcontroller Family
For each timer, there exists a built-in variable that indicates when the timer is in use. For example,
Register.Timer0Busy is a Boolean value that indicates when Timer0 is 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
Routine
TimerSpeed Value
ADCtoCom1()
Com1toDAC()
CountTransitions()
TimerSpeed1¹
FreqOut()
Get1Wire()
Get1WireByte()
Get1WireData()
I2CCmd()²
TimerSpeed1
I2CGetByte()²
TimerSpeed1
I2CPutByte()²
TimerSpeed1
InputCapture()
TimerSpeed1
InputCaptureEx()
TimerSpeed1
OutputCapture()
TimerSpeed1
OutputCaptureEx()
TimerSpeed1
OpenPWM()
RCTime()
TimerSpeed2¹
PlaySound()
PulseIn()
TimerSpeed2¹
PulseOut()
TimerSpeed2¹
Put1Wire()
Put1WireByte()
Put1WireData()
PWM()
Reset1Wire()
ShiftIn()
TimerSpeed1
ShiftInEx()
TimerSpeed1
ShiftOut()
TimerSpeed1
ShiftOutEx()
TimerSpeed1
X10Cmd()
Notes:
1)
The timer frequency is scaled. See below.
2)
The timer is used only for channels 1-4.
The default value of Register.TimerSpeed1 is 1 and the default value for Register.TimerSpeed2
is 2. 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. The divisor specified is applied to the
CPU clock frequency to yield the I/O Timer clock frequency. For compatibility with BasicX (but only for ZX
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