ARM instructions exceptions !!

Hi :

I am studying the ARM architecture reference manual recently because my work is about the simulation of ARM7TDMI based processor core.

There are so many instruction exceptions;

for example: when using the ldm instruction, if the base register Rn is also in the register list, an exception of UNPREDICTABLE will appear.

Is there a list to show all the exceptions I must pay attention to when tesing ??


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Isn't the architecture manual exactly that list you're asking about?

Hans-Bernhard Broeker (
Even if all the snow were burnt, ashes would remain.
Reply to
Hans-Bernhard Broeker

Sorry !! I mean overall factors to cause the UNPREDICTABLE result. Most instructions have some UNPREDICTABLE situations, and I want to know if there exists a list to show all the factors to result in UNPREDICTABLE.

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Just go and pick all of them for ARM ARM.

Please note that UNPREDICTABLE means really it - it is very probably different on different chips and maybe also different depending on the conditions before the UNPREDICTABLE condition.

The UNPREDICTABLE conditions leave the chip designer's hands free to optimize the logic in the way he deems fit.


Tauno Voipio tauno voipio (at) iki fi

Reply to
Tauno Voipio

The ARM ARM could have made things more clear by referring to the so-called exceptions as being implementation-defined. Most of the "exceptions" typically are for someone using the PC as one of the operands. These will occur most often by coding mistake, so all bets are off as to what will happen.

Reply to
Everett M. Greene

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