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Architectures and Processors forum What will happen if Cortex-M0 fetches 0xFFFF_FFFF as an instruction ?

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What will happen if Cortex-M0 fetches 0xFFFF_FFFF as an instruction ?

stevens.wang over 8 years ago

Dear Guys,

In typical SoC product, the FLASH memory is initially empty after being shipped from factory, in which the data are all "0xFFFF_FFFF".

I am curious how Cortex-M0 deals with the undefined instruction data "0xFFFF_FFFF" after being fetched from empty FLASH, before it is programmed by tools.

Does anyone know that ?

Stevens

Thanks a lot

0 Martin Weidmann over 8 years ago

As the value doesn't map to a "valid" opcode, you'd get an exception due to an Undefined Instruction. Take a look at section B1.5.14 (Fault behavior) of the ARMv6-M Architecture Reference Manual. Or alternatively...
Cortex-M0 Devices Generic User Guide: 2.4. Fault handling
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0 stevens.wang over 8 years ago in reply to Martin Weidmann

Understood. Thanks a lot, Martin. (^_^)
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