Changes
6502
,/* Memory Access */
Instructions PHA and PHP push the accumulator and processor status onto the stack, while PLA and PLP pull them back. Subroutine calls with JSR store the return address on the stack, and RTS retrieves it to continue execution. Similarly, interrupts (BRK) push the program counter and status, while RTI restores them.
All I/O operations are memory-mapped. There are no port-based I/O instructions. Memory-mapped ports often have different properties than normal RAM:
* The contents of a port can be updated by the hardware. Reading a port will not always return the same value each time it is read.
