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Update ghost.md
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shazz authored Aug 17, 2024
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Expand Up @@ -342,7 +342,9 @@ So in order, the reset vector routine:
1. Set a specific target address: end of ST RAM (`PHYSTOP` (`0x42E`) depends on model 520, 1040..., for example that's 0x80000 on a 520, 0x100000 on a 1040), then minus 0x8000 and minus 0x200 (basically 32KB + 512 bytes before the end of the available memory)
1. It has to be on a 0x200 (512) bytes boundary
1. It is better to be near the end of the memory to limit chances to be overlapped and erased after reset
1. You'll notice the memory substraction in done in 2 steps and not a "simple" SUBA.L #$8200,A1. Why? It looks to be linked to 68K SUBA opcode which considered the offset as signed as $8000 is half a word. I need to investigate what the assember generates for the size specification:
1. You'll notice the memory substraction in done in 2 steps and not a "simple" SUBA.L #$8200,A1.

Why? It looks to be linked to 68K SUBA opcode which considered the offset as signed as $8000 is half a word. I need to investigate what the assember generates for the size specification:

```
Object Code: 1001 ddds 11 ff ffff
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