Todays Emm disasmebled

[nozzer]

Is there a simple explanation why the value is 3 and not 6 as I would have thought?

The simple explanation is that its not a memory location. Its a control register. That means it may have strange qualities such as certain bits being write only (if read, only ever return a fixed bit value) or certain bits being protected and only accessible when another bit is written within so many cycles etc........

 

[tonmedia11]

Almost there, keys being written but first byte slightly wrong - probably a silly error somewhere on my part. Will put the coding up later if I can't solve it myself.

 

[IAmATeaf]

The simple explanation is that its not a memory location. Its a control register. That means it may have strange qualities such as certain bits being write only (if read, only ever return a fixed bit value) or certain bits being protected and only accessible when another bit is written within so many cycles etc........

Is there anything I can read up about this, had a look at all the FAQs I have and nothing is really mentioned about it.

 

[IAmATeaf]

Almost there, keys being written but first byte slightly wrong - probably a silly error somewhere on my part. Will put the coding up later if I can't solve it myself.

What I did initially was to not do the XOR but simply get the code to write the keys as they are in the EMM to confirm I had the correct offsets, then I added/uncommented the XOR bit. Remember you need to XOR with 0x6.

 

[nozzer]

Is there anything I can read up about this, had a look at all the FAQs I have and nothing is really mentioned about it.

Can't think of anything specific at the moment but most embedded processors have registers that may, at first glance, appear to exhibit strange behaviour.

Registers that control hardware like timers or Uarts etc are usually good at doing odd things. For instance, to clear a timer you may have to set a bit to 1 but the hardware will probably set the bit back to 0 in the next cycle (signifying that the reset has occured). Think of this particular type of register bit being a momentary switch rather than the toggle switch of a normal memory bit.

 

[tonmedia11]

Not exactly sure what happened first time round using xor 0x06 but when they were removed it was exactly same as the bytes dump. Re-instated the EOR command and all sorted now. Thanks to all the guys who contributed to the thread.

 

[IAmATeaf]

Not exactly sure what happened first time round using xor 0x06 but when they were removed it was exactly same as the bytes dump. Re-instated the EOR command and all sorted now. Thanks to all the guys who contributed to the thread.

Well done mate : multi :

 

[fes_786]

Not exactly sure what happened first time round using xor 0x06 but when they were removed it was exactly same as the bytes dump. Re-instated the EOR command and all sorted now. Thanks to all the guys who contributed to the thread.

congrats m8

cheers

its hardwork just trying to understand the code and thats the old keyroll 3...lol


well im still gona try this out

and will keep following the tuts

and by next hit on these i should be of more help

cheers

 

[tonmedia11]

Thanks again guys, but the work here was pretty much done by IAmATeaf. Fes is see you're having a look at grape/funcard, if you want a look at at what i compiled here with some basic explanations of some of the stages for comparisons send me a pm

 

[the_blackadder1980]

big thanks guys, hopefully i will be a lot quicker next time and wont need a tutorial by my side. thanks for atmega and fun fixes. you have probably just saved me another 6-7 hours on the computer and a lot off brainache.

 

[tonmedia11]

I apologise for not adding any relevent info, but I just couldn't resist seeing a very important thread at the top for a minute or two rather than on the second page after all the thank you posts from those who decided just to sit and wait.

 

[nozzer]

Well done people !

Brings a tear to my eyes seeing the pupils from last time becoming the new teachers