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Renesas Electronics America - Knowledgebase

Cause of Undefined Instruction Exception

Last Updated:03/08/2018


What kind of error is an undefined instruction exception?  What are the possible causes and how can they be investigated?


An undefined instruction exception occurs when the execution of an undefined instruction (unimplemented instruction) is detected. Generally, undefined instruction exceptions do not occur when a program is described in C or an assembler without a compiler error.  

Undefined instruction exceptions may occur from the following reasons:
・Various noise
・Data corruption 
・Device destruction 
・Stack not set
・Stack overflow
・A target device does not correspond to the endian setting of debugger
・Jump to the wrong destination
・Flash memory access wait is not set

Please check the following:
・If built-in flash memory program is executing under P/E mode
・If the stack size is appropriate
・If ROM/RAM section is allocated correctly  
・If a target device corresponds to the endian setting of the debugger
・If clock-related register is set correctly

Suitable Products
RX Family