Virtual Ports

The Virtual Port registers map the most frequently used regular Port registers into the bit-accessible I/O space. Writing to the Virtual Port registers has the same effect as writing to the regular registers, but allows for memory-specific instructions, such as bit-manipulation instructions, which are not valid for the extended I/O memory space where the regular Port registers reside.
Table 1. Virtual Port Mapping
Regular Port Register Mapped to Virtual Port Register
PORT.DIR VPORT.DIR
PORT.OUT VPORT.OUT
PORT.IN VPORT.IN
PORT.INTFLAG VPORT.INTFLAG