Operating Systems Memory-Mapped 1/0 c Each controller has a few registers that are used for communication with cpu g Write into these registers os can command the device to deliver data accept data, switch itselfon or off, or otherwise perform some action G Read from these registers: OS can learn what the devices state is whether it is prepared to accept a new command, and so on c In addition to the control registers, many devices have a data buffer that the os can read and write(e.g video ram) c Q: How the CPU communicates with the control registers and the device data buffer? Gao Haichang, Software School, Xidian UniversityOperating Systems Gao Haichang , Software School, Xidian University 8 Memory-Mapped I/O  Each controller has a few registers that are used for communication with CPU.  Write into these registers: OS can command the device to deliver data, accept data, switch itself on or off, or otherwise perform some action.  Read from these registers: OS can learn what the device’s state is, whether it is prepared to accept a new command, and so on.  In addition to the control registers, many devices have a data buffer that the OS can read and write (e.g. video RAM).  Q: How the CPU communicates with the control registers and the device data buffer?