6.5.1. Methods of installing exception handlers

Exception handlers can be installed in the following ways:

Branch instruction

This is the simplest way to reach the exception handler. Each entry in the vector table contains a branch to the required handler routine. However, this method does have a limitation. Because the branch instruction only has a range of 32MB relative to the PC, with some memory organizations the branch might be unable to reach the handler.

Load PC instruction

With this method, the PC is forced directly to the handler address by:

  1. Storing the absolute address of the handler in a suitable memory location (within 4KB of the vector address).

  2. Placing an instruction in the vector that loads the PC with the contents of the chosen memory location.

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