annotate src/startup.s @ 6:862f8a034cae
expanding the megadrive code
| author |
John Tsiombikas <nuclear@member.fsf.org> |
| date |
Sat, 11 Feb 2017 08:56:42 +0200 |
| parents |
54739a11be66 |
| children |
8253942b0a1a |
| rev |
line source |
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1 .text
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2 .extern main
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3
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4 .global start
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5 .global halt_cpu
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6 start:
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7 | copy .data section from ROM to RAM
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8 move.l #_data_lma, %a0
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9 move.l #_data_start, %a1
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10 move.l #_data_end, %a2
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11 cmp.l %a1, %a2
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12 beq.s 1f | skip data copy if the section is empty
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13 0: move.l (%a0)+, (%a1)+
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14 cmp.l %a1, %a2
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15 bne.s 0b
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16 1:
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17
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18 | zero the .bss section
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19 move.l #_bss_start, %a0
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20 move.l #_bss_end, %a1
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21 cmp.l %a0, %a1
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22 beq.s 1f | skip bss zeroing if the section is empty
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23 0: clr.l (%a0)+
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24 cmp.l %a0, %a1
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25 bne.s 0b
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26 1:
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27 jsr main
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28 halt_cpu:
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29 stop #0x2700
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