Altera DE1-SoC - Page 26

DE1-SOC COMPUTER SYSTEM WITH NIOS II For Quartus II 15.0
#include "nios2_ctrl_reg_macros.h"
/* function prototypes */
void main(void);
void interrupt_handler(void);
void interval_timer_isr(void);
void pushbutton_ISR(void);
/* The assembly language code below handles Nios II reset processing */
void the_reset (void) __attribute__ ((section (".reset")));
void the_reset (void)
/*******************************************************************************
* Reset code; by using the section attribute with the name ".reset" we allow the linker program
* to locate this code at the proper reset vector address. This code just calls the main program
******************************************************************************/
{
asm (".set noat"); // magic, for the C compiler
asm (".set nobreak"); // magic, for the C compiler
asm ("movia r2, main"); // call the C language main program
asm ("jmp r2");
}
/* The assembly language code below handles Nios II exception processing. This code should not be
* modified; instead, the C language code in the function interrupt_handler() can be modified as
* needed for a given application. */
void the_exception (void) __attribute__ ((section (".exceptions")));
void the_exception (void)
/*******************************************************************************
* Exceptions code; by giving the code a section attribute with the name ".exceptions" we allow
* the linker to locate this code at the proper exceptions vector address. This code calls the
* interrupt handler and later returns from the exception.
******************************************************************************/
{
asm (".set noat"); // magic, for the C compiler
asm (".set nobreak"); // magic, for the C compiler
asm ( "subi sp, sp, 128");
asm ( "stw et, 96(sp)");
asm ( "rdctl et, ctl4");
asm ( "beq et, r0, SKIP_EA_DEC"); // interrupt is not external
asm ( "subi ea, ea, 4"); /* must decrement ea by one instruction for external
* interrupts, so that the instruction will be run */
Figure 22. Reset and exception handler C code (Part a).
26 Altera Corporation - University Program
2015