Zilog Z8F0130 - Manual (Page 227)

UM013037-1212 Monitor Function Support
Zilog Developer Studio II – Z8 Encore!
User Manual
203
SET_VECTOR Intrinsic Function
SET_VECTOR can be used to specify the address of an interrupt handler for an interrupt
vector. Because the interrupt vectors of the Z8 Encore! microcontroller are usually in
ROM, they cannot be modified at run time. The SET_VECTOR function works by switch-
ing to a special segment and placing the address of the interrupt handler in the vector table.
No executable code is generated for this statement.
The following is the SET_VECTOR intrinsic function prototype:
intrinsic void SET_VECTOR(int vectnum ,void (*hndlr)(void));
An example of the use of SET_VECTOR is as follows:
#include

extern void interrupt isr_timer0(void);

void main(void)

{

SET_VECTOR(TIMER0, isr_timer0);

}
See the SET_VECTOR section on page 237 for supported values of vectnum.
_At Keyword
The _At keyword, described in the Placement Directives section on page 206, can be used
in conjunction with the interrupt keyword to associate an interrupt handler with an
interrupt vector. Because the interrupt vectors of the Z8 Encore! microcontroller are usu-
ally in ROM, only one handler can be associated with an interrupt vector.
For example:
#include

void interrupt isr_timer0(void) _At TIMER0

{

}
Monitor Function Support
A special function qualifier type is provided to support users who are interested in creating
a real-time operating system (RTOS) kernel for the Z8 Encore!. Functions defined with
this qualifier are treated differently from other functions at the point of function entry and
function exit. At function entry, the global interrupt status is saved on the stack and inter-
rupts are then disabled, before any other action is taken including the setup of the normal
stack frame, if any. Upon exit from a monitor function, the last thing that happens before
returning from the function is that the previous interrupt state is restored from the stack.
These operations are useful or perhaps even critical in designing an RTOS and also pro-
vide the fastest possible way of disabling interrupts in a critical section of kernel code.
To define a function of this type, use the _monitor pragma, as in the following code: