ZBasic Language Reference
15
ZBasic Microcontrollers
Examples
Option ExtRamConfig On
Option ExtRamConfig &H0084 ' enable with 1 wait state (ATmega)
Option RamSize <constant-expression>
Default: (see text)
The compiler compares the aggregate size of the statically allocated data items to the amount of RAM
available in the target device. If the aggregate size is too large, the compiler issues a warning to that
effect. For ZBasic devices that support external RAM (e.g. ZX-1281), the compiler must know the actual
size of User RAM (including external RAM) in order to avoid generating meaningless warnings. That is
the purpose of this directive, which may only be used on ZBasic devices that support external RAM. The
example below shows the simplest way of specifying the augmented User RAM size. The example is for
the case where the maximum amount of additional RAM was added.
Example
Option RamSize 65536 – Register.RamStart
Option HeapSize <constant-expression>
Default: (see text)
This directive controls the allocation of RAM between the string heap and the Main() task stack. The
effect is to set a hard limit beyond which the heap will not grow, thereby preventing the heap from
encroaching on the Main() task stack. If a size less than the minimum size (which varies by device) is
specified, the minimum is used instead. Also, for devices with external RAM, the special value of 65535
(&HFFFF) can be used to specify that all external RAM should be used for the heap. See the section on
setting heap and task stack sizes for more information including the default heap size.
For VM mode devices the directive has an additional effect. When the compiler performs various checks
regarding the use of RAM, it takes into account an amount of RAM reserved for the heap (from which
memory for strings, for example, is allocated). The size specified for the heap will effect whether the
compiler will issue a warning about excessive use of RAM in a particular circumstance.
Example
Option HeapSize 500
Option HeapReserve <constant-expression>
Default: (see text)
After compilation, the compiler analyzes the use of RAM and compares it to the amount of RAM available
on the target device. If a specific task stack size is specified for the Main() task, the compiler adds the
amount of statically allocated data, the Main() task stack size and the minimum heap size and compares
this total to the amount of available RAM. If the aggregate total exceeds the available RAM an error
message will be issued.
This directive allows you to specify the minimum space you want to reserve for the heap. See the section
on setting heap and task stack sizes for more information including the default heap size.
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