| ??? 09/10/05 07:52 Read: times |
#100892 - If you want a proper answer... Responding to: ???'s previous message |
Neil Kurzman said:
In any case You Need a general embedded or X86 embedded group. Exactly - why would you expect an 8051 "expert" to answer detailed x86 questions?! If he'd asked a proper, on-topic 8051 question, I'd have the "bible," data sheets etc to look it up and give a definitive (hopefully!) answer - all this x86 stuff is just from memory... In X86 in ASM or a 'C' near pointer (a 'C' far pointer has no problem) if you inc a pointer set to 0xFFFF you end up at the bottem of the segment. so an increment at FFFF:FFFF gives you FFFF:0000 not 0000:0000. That sounds right - because the 16-bit Offset rolls-over from FFFF to 0000 independently of the 16-bit Segment. That's why I specifically chose the example of the 16-bit Offset incrementing from 000F to 0010, giving a 20-bit EA roll-over from FFFFF to 00000. I think that's right, isn't it? Of course, a joy of the Segmented architecture is that you're not restricted to rollover problems just at the end of memory - you can have a rollover at the end of any paragraph in memory...! On X86 0000:0000 would not be the boot code. the reset vector is at the top of memory. It must have a jump the the start of code.
the bottom of memory for AM188 is the Interupt Vector Table. Yes - see http://www.8052.com/forumchat/read.phtml?id=100784 and http://www.8052.com/forumchat/read.phtml?id=100782 MOV@R0 on the '52 would give you similar results. Not quite - PDATA pages in the 8051 do not overlap... Anyhow, the OP seems to have lost interest now. |
| Topic | Author | Date |
| Micro Controller powered? | 01/01/70 00:00 | |
| bible study time? | 01/01/70 00:00 | |
| Reboot ? | 01/01/70 00:00 | |
| See reply (Off-Topic) | 01/01/70 00:00 | |
| Not A PC | 01/01/70 00:00 | |
| Reboot doubt | 01/01/70 00:00 | |
| Off Topic. | 01/01/70 00:00 | |
| Rampant code execution | 01/01/70 00:00 | |
| CS:IP | 01/01/70 00:00 | |
| Irrelevant? | 01/01/70 00:00 | |
| irrelevent: irrelevent? | 01/01/70 00:00 | |
| TOTALLY irrelevant, at least at a '51 fo | 01/01/70 00:00 | |
| Already established! | 01/01/70 00:00 | |
| Wrong | 01/01/70 00:00 | |
| You Sure? | 01/01/70 00:00 | |
If you want a proper answer... | 01/01/70 00:00 |