ZBasicRef - page 103 of 172

ZBasic Language Reference

ZX Microcontroller Family

Declare index as Integer Attribute(Constant)

If the external variable declaration has both an Alias and and Attribute specified, they may occur in either

order. For compatibility with the Declare statement in Visual Basic, the Alias specification for an external

subroutine or function declaration may be placed between the routine name and the opening parenthesis

of the parameter list. The form shown above, however, is the recommended syntax because it is more

consistent with the other uses of the Alias keyword.

4.3 Defining Interrupt Service Routines

For the native mode devices you may write special-purpose code to service hardware interrupts. This

may be useful, for example, to add some interrupt-driven capability to your program that is not directly

supported by ZBasic. The syntax for defining an interrupt service routine is similar to that for defining a

subroutine, illustrated here by example. Note that the definition of an ISR does not allow parameters but

the parentheses are, nonetheless, required.

ISR Timer1_CompB()

' place the ISR code here

The ISR name following the ISR keyword must be valid for the underlying processor, a list of which is

shown in the table below. The ISR names are not case sensitive. More specific details about each

interrupt may be found in the datasheet for the corresponding AVR processor. The shaded entries in the

table below denote ISR names that may not be used because their functionality is essential to the

operation of the ZX infrastructure. For other ISR names, you may define an ISR provided that it does not

conflict with an ISR that is needed for System Library routines that you use in the application. For

example, you may provide an ISR for the Timer1 Input Capture interrupt as long as you do not use the

ZBasic System Library routine InputCapture() in your program. In the table below, the superscript, if any,

indicates an ISR that may be automatically supplied by the compiler. The notes below the table describe,

in general terms, when they might be automatically supplied. The descriptions of the System Library

routines describe with more specificity which ISRs they require, if any, and the conditions under which

they will be required.

Available ISR Names by CPU Type