Design MCU based A/B access switch to CF-card

Let's say that we have CF-card, and we have two devices that need to have full R/W access to it, one device at the time. Hence we would need a simple circuit that control access to CF card either from device A or device B. Note: dynamic switching is not needed. Switching can be done at reset, ie. at the press of the button MCU simply memorizes that another device should have granted access, and enables access to that device after reset. We would need simple schematic / circuit diagram only. If that stage is accomplished successfully, other assignments will follow.