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Post Info TOPIC: offset data in external memory?


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offset data in external memory?


Hi guys, ... it appears on the surface that the 7052 is grabbing data from external memory ...

ROM:0000A21A mova @(8,pc), r0 ; [0000A224] = h'24001E
ROM:0000A21C mov.w @(r0,r1), r0
ROM:0000A21E braf r0
ROM:0000A220 nop

there's a loop here with r1 starting at 0 and incrementing by 2 each time through the loop, for a total of 16 loops.

looks like it's picking up an offset from external memory (24001E is way outside the ROM and RAM areas) to perform a different branch each time through the loop

any idea where this external memory is? external to the 7052? - or inside the 7052 as a 'special' for denso?

might have to redump the 7052 with some attention to the area around 24001E ...??

cheers,
Mark

edit: I ought to think before I post. The MOVA instruction I think puts the calculated address into r0, not the contents of the calculated address ... IDA fooled me here by indicating what the calculated address contains, and I blindly assumed that was what ended up in r0 ... so please forget my silly remarks about data living in external memory ... my apologies

-- Edited by bozo at 12:38, 2007-12-23

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Well, maybe its not so far fetched. I recall finding out DMA source address being mapped to certain ram areas, almost like some of the functions are copied to ram before executing. Anyway have not found anything outside the known address space so far.

I have found that I must be very carefull  weather the address used is byte, word or longword. IDA is errorprone on that.




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