2.2.1. Data Abort model

The ARM9E-S implements the base restored Data Abort model, which differs from the base updated Data Abort model implemented by ARM7TDMI.

The difference in the Data Abort model affects only a very small section of operating system code, the Data Abort handler. It does not affect user code. With the base restored Data Abort model, when a Data Abort exception occurs during the execution of a memory access instruction, the base register is always restored by the processor hardware to the value the register contains before the instruction is executed. This removes the requirement for the Data Abort handler to unwind any base register update that might have been specified by the aborted instruction.

The base restored Data Abort model significantly simplifies the Data Abort handler software.

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