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Andy Neil
09/08/05 11:46
Read: 1076 times
Basingstoke
Uk


 
#100828 - Wrong
Responding to: Abhishek Singh's previous message
Abhishek Singh said:
ok but here op talks about the IP roll over

No, he didn't.
He didn't even mention registers at all:
Rupesh Deenadayalan said:
... when the microcontroller reaches to fffffth memory location it rolls over to 00000th memory location ...


The 20-bit Effective Address (ie, the physical memory address) is calculated from the 16-bit Segment & Offset as follows:
EA = Segment*16 + Offset
See: http://www.ece.msstate.edu/~reese/EE...de0019.htm

So, if Segment=FFFF AND Offset=000F,
EA = FFFF0 + 000F = FFFFF
If the Offset is now incremented by one to 0010, we get
EA = FFFF0 + 0010 = 00000 (botton 20 bits)
So incrementing the Offset can cause the Effective Address to roll-over from FFFFF to 00000.

List of 16 messages in thread
TopicAuthorDate
Micro Controller powered?      Rupesh Deenadayalan      09/06/05 00:10      
   bible study time?      Andy Neil      09/06/05 01:22      
      Reboot ?      Rupesh Deenadayalan      09/08/05 00:53      
         See reply (Off-Topic)      Andy Neil      09/08/05 01:41      
   Not A PC      Neil Kurzman      09/06/05 09:35      
      Reboot doubt      Rupesh Deenadayalan      09/08/05 00:35      
         Off Topic.      Andy Neil      09/08/05 00:47      
            Rampant code execution      Andy Neil      09/08/05 01:00      
            CS:IP      Abhishek Singh      09/08/05 06:45      
               Irrelevant?      Andy Neil      09/08/05 08:47      
                  irrelevent: irrelevent?      Abhishek Singh      09/08/05 09:16      
                     TOTALLY irrelevant, at least at a '51 fo      Erik Malund      09/08/05 09:39      
                        Already established!      Andy Neil      09/08/05 10:37      
                     Wrong      Andy Neil      09/08/05 11:46      
                        You Sure?      Neil Kurzman      09/09/05 12:45      
                           If you want a proper answer...      Andy Neil      09/10/05 01:52      

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