Microcontrollers don't need additional ports either. Take a look a the ARMv7-M status/control register. It has a few bits of state to allow ldm, stm, and if-t

Microcontrollers don't need additional ports either. Take a look a the ARMv7-M status/control register. It has a few bits of state to allow ldm, stm, and if-then to be resumed in-place. At that scale, those mechanisms aren't micro-coded, they are state-machined. You just have to restore the state machine.