annotate src/startup.s @ 9:6ecf2f3ff05a
- better pad input handling
- switch between 28 and 30 vertical tiles by pressing C
| author |
John Tsiombikas <nuclear@member.fsf.org> |
| date |
Sat, 24 Jun 2017 00:33:10 +0300 |
| parents |
b22bc95f0cc0 |
| children |
54caa2b214ca |
| rev |
line source |
|
nuclear@4
|
1 | vi:filetype=gas68k:
|
|
nuclear@0
|
2 .text
|
|
nuclear@0
|
3 .extern main
|
|
nuclear@0
|
4
|
|
nuclear@0
|
5 .global start
|
|
nuclear@0
|
6 .global halt_cpu
|
|
nuclear@0
|
7 start:
|
|
nuclear@1
|
8 jsr disable_intr
|
|
nuclear@0
|
9
|
|
nuclear@0
|
10 | copy .data section from ROM to RAM
|
|
nuclear@0
|
11 move.l #_data_lma, %a0
|
|
nuclear@0
|
12 move.l #_data_start, %a1
|
|
nuclear@0
|
13 move.l #_data_end, %a2
|
|
nuclear@0
|
14 cmp.l %a1, %a2
|
|
nuclear@0
|
15 beq.s 1f | skip data copy if the section is empty
|
|
nuclear@0
|
16 0: move.l (%a0)+, (%a1)+
|
|
nuclear@0
|
17 cmp.l %a1, %a2
|
|
nuclear@0
|
18 bne.s 0b
|
|
nuclear@0
|
19 1:
|
|
nuclear@0
|
20
|
|
nuclear@0
|
21 | zero the .bss section
|
|
nuclear@0
|
22 move.l #_bss_start, %a0
|
|
nuclear@0
|
23 move.l #_bss_end, %a1
|
|
nuclear@0
|
24 cmp.l %a0, %a1
|
|
nuclear@0
|
25 beq.s 1f | skip bss zeroing if the section is empty
|
|
nuclear@0
|
26 0: clr.l (%a0)+
|
|
nuclear@0
|
27 cmp.l %a0, %a1
|
|
nuclear@0
|
28 bne.s 0b
|
|
nuclear@0
|
29 1:
|
|
nuclear@0
|
30
|
|
nuclear@0
|
31 | setup the stack pointer stack
|
|
nuclear@0
|
32 move.l #_stacktop, %sp
|
|
nuclear@0
|
33 | now that we have a stack, we can enable interrupts
|
|
nuclear@1
|
34 jsr enable_intr
|
|
nuclear@0
|
35
|
|
nuclear@0
|
36 jsr main
|
|
nuclear@0
|
37 halt_cpu:
|
|
nuclear@0
|
38 stop #0x2700
|
