Changes
/* The Vectored Interrupt Bug */
The bug relates to the raster interrupt. When a raster interrupt is acknowledged sometimes the vector will be 6 (for raster interrupt) or 4 (for dma channel 0 - the lowest priority interrupt).
* If the instruction at the time of interrupt acknowledge is located in a memory region where A13=0 then the bug happens. The bug is not dependent on RAM or ROM or I register value. The location of the interrupt handler code is also not important. The location of the instruction is important. The bug also doesn't seem to happen when the instruction is purely based on opcode read operation (e.g. single byte with opcodes that don't use memory read/write or don't contain a memory)read/write when fetching the opcode. Single byte instructions are fine including HALT. However, it is difficult to code in a way to workaround the issue in this way.
* If the instruction at the time of interrupt acknowledge is located in a memory region where A13=1 then the bug doesn't happen. Therefore to workaround the issue put your code between &2000-&3fff, &6000-&7fff, &a000-&bfff, &e000-&ffff. You can place your I value anywhere and the code for your interrupt handlers can
be anywhere.
== Technical ==
