megadrive_test2
view src/startup.s @ 12:54caa2b214ca
TMSS code
| author | John Tsiombikas <nuclear@member.fsf.org> |
|---|---|
| date | Wed, 26 Dec 2018 04:39:09 +0200 |
| parents | 72ab63f262bf |
| children |
line source
1 | vi:filetype=gas68k:
2 .text
3 .extern main
5 .global start
6 .global halt_cpu
7 start:
8 jsr disable_intr
10 | write SEGA to 0xa14000 to convience the TMSS to run us
11 move.l 0x100, %d0
12 move.l %d0, 0xa14000
14 | copy .data section from ROM to RAM
15 move.l #_data_lma, %a0
16 move.l #_data_start, %a1
17 move.l #_data_end, %a2
18 cmp.l %a1, %a2
19 beq.s 1f | skip data copy if the section is empty
20 0: move.l (%a0)+, (%a1)+
21 cmp.l %a1, %a2
22 bne.s 0b
23 1:
25 | zero the .bss section
26 move.l #_bss_start, %a0
27 move.l #_bss_end, %a1
28 cmp.l %a0, %a1
29 beq.s 1f | skip bss zeroing if the section is empty
30 0: clr.l (%a0)+
31 cmp.l %a0, %a1
32 bne.s 0b
33 1:
35 | setup the stack pointer stack
36 move.l #_stacktop, %sp
37 | now that we have a stack, we can enable interrupts
38 jsr enable_intr
40 jsr main
41 halt_cpu:
42 stop #0x2700