 |
 |
|
 |
 |
ZBasic System Library
301
ZX Microcontroller Family
WaitForInterrupt
Type
Subroutine
Invocation
WaitForInterrupt(mode)
WaitForInterrupt(mode, intNum)
Parameter
Method
Type
Description
mode
ByVal
Byte
A value specifying what action will trigger the interrupt. See the
discussion below.
intNum
ByVal
Byte
A designator for the interrupt to await (see discussion below).
Discussion
This routine allows a task to suspend itself and wait for an interrupt. The particular interrupt awaited
depends on the intNum designator combined with the mode value. There are three general sources of
interrupts that can be awaited: external interrupts, analog comparator interrupts and pin change
interrupts.
External Interrupts 0-7 (ATmega-based devices)
A task may await an external interrupt by specifying the value 0 through 7 (corresponding to external
interrupts 0-7, respectively) for the intNum parameter. In this case, the allowable values for the mode
parameter and their respective meanings are given in the table below. Note, however, that some devices
support only a subset of the hardware interrupt channels. See the table in the Resource Usage section
for details of the supported interrupt channels and the interrupt input pin for each device.
Hardware Interrupt Mode Values
Value
Built-in Constant
Interrupt Trigger
&H10
zxPinLow
A low level on the interrupt pin.
&H14
zxPinChange
Any logic level change on the interrupt pin.
&H18
zxPinFallingEdge
A high to low transition on the interrupt pin.
&H1C
zxPinRisingEdge
A low to high transition on the interrupt pin.
All other values are reserved for future use. For compatibility with BasicX, there are similarly named built-
in constants that begin with the prefix bx instead of zx except that there is no equivalent for
zxPinChange. Additionally, on mega32-based devices, Interrupt 2 is not capable of the first two trigger
modes; it can only be triggered on a rising edge or a falling edge.
The built-in constants WaitInt0 through WaitInt7 may be used to specify the intNum parameter. If
no intNum parameter is given, Interrupt 1 is assumed (for compatibility with BasicX). This is equivalent
to using WaitForInterrupt(mode, 1).
Pin Change Interrupts (ATmega-based devices)
For some ZX models based on the ATmega processors, a task may await a state change on one or more
pins of an I/O port. This mode is selected by specifying a special value for the intNum parameter
according to the tables below for the respective processor types.
intNum Values for Pin Change Interrupts
Value
Built-in Constant
Trigger – mega644,
mega644P, mega1284P
Trigger – mega328P
&H20
WaitPinChangeA
Pin change on Port A
&H21
WaitPinChangeB
Pin change on Port B
Pin change on Port B
|
 |
|