- .equ STACK_TOP, 0x20000800
+/* (CC-BY-NC-SA) ROBIN KRENS - ROBIN @ ROBINKRENS.NL
+ *
+ * $LOG$
+ * 2019/7/20 - ROBIN KRENS
+ * Initial version
+ *
+ * $DESCRIPTION$
+ */
+
+/* _start sets up the stack and jumps to the reset vector */
+
+ .equ STACK_TOP, 0x20010000 /* placed at 64kB, top of SRAM */
.text
.global _start
+ .global reset, nmi, hardfault
.code 16
.syntax unified
_start:
- .word STACK_TOP, start
- .type start, function
+ .word STACK_TOP, reset, nmi, hardfault
+ .type reset, function
+
+/* A reset vector (or bootcode) will call main in main.c
+ this is the so called 'entry to C' */
+reset:
+ b main
+ b reset
-/* Start of main program */
-start:
- movs r0, #5
- movs r1, #1
-loop:
- adds r1, r0
- subs r0, #1
- bne loop
- /* Result is now in R1 */
- ldr r0, =Result
- str r1, [r0]
+/* These are consequently the nmi and hardfault vector handlers
+ before booting and entering main, these can actually be called
+ (machine somehow has a failure). That's why they are included here.
+ Later the interrupt vector
+ will be relocated to SRAM and the will be copied / modified. */
-deadloop:
- b deadloop
+nmi:
+ b nmi
- .data
- .word 0 /* add two words*/
- .word 0
-Result:
- .word 0 /* results now is in 0x20000008 (0x20000000 + 2 w) */
+hardfault:
+ b hardfault
+
.end