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ZBasic System Library
13
ZX Microcontroller Family
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 System
Library routines that require that timer from functioning.
Processor Speed Issues
Although the standard clock speed for ZX devices is 14.7456MHz, special versions are available that run
slower and faster. The table below summarizes the differences that arise due to the difference in
operating speed.
Processor Speed Variations
Issue
7.3728MHz
14.7456MHz
18.432MHz
RTC Tick Frequency
512 Hz
512 Hz
500 Hz
RTC Fast Tick Frequency
512 Hz
1024 Hz
1K Hz
RTC Timer Frequency
115.2 KHz
230.4 KHz
72K Hz
Multi-tasking Time Slice
1.95 mS
1.95 mS
2.0 mS
Default TimerSpeed1 Units
135.6 nS
67.8 nS
54.4 nS
Default TimerSpeed2 Units
1.085 µS
1.085 µS*
434 nS
CountTransitions() Sample Rate
204.8 KHz
409.6 KHz
512 KHz
Note, particularly, that the value for TimerSpeed2 at 14.7456MHz is scaled to match the value
corresponding to operating at 7.3728MHz. This is done for compatibility with BasicX devices that operate
at the latter speed. Consult the preceding sections for information on which routines use the
TimerSpeed1 and TimerSpeed2 values.
It is highly recommended to use the built-in values Register.CPUFrequency,
Register.RTCTickFrequency, and Register.RTCTimerFrequency instead of using hard-coded
values. Doing so also simplifies code that must run on multiple devices that operate at different speeds.
See the descriptions in the ZBasic Language Reference Manual for more details.
Detailed Descriptions
In the descriptions that follow, the parameter types that are accepted by each routine are described.
Some parameters accept a specific fundamental data type while others may accept a few similar types.
Others accept virtually any parameter type. In order to more succinctly describe the types of parameters
accepted, some descriptive type categories are used. For example, the category integral is used to
connote those types that have the integral characteristic, such as Byte, Integer, UnsignedInteger,
Long and UnsignedLong. The table below indicates which types belong to which categories.
Type Category Membership
Type/Category
any type
integral
int8/16
int16
int32
any 32-bit
signed
numeric
Boolean
x
Bit
x
x
x
x
Nibble
x
x
x
x
Byte
x
x
x
x
Integer
x
x
x
x
x
x
UnsignedInteger
x
x
x
x
x
Enum
x
Long
x
x
x
x
x
x
UnsignedLong
x
x
x
x
x
Single
x
x
x
x
String
x
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