Nonvolatile memory device using separate command/address interface, method of operating the memory device, and storage device including the memory device

A nonvolatile memory device configured to receive a command and an address via a first bus and transmit and receive data to and from an external device that is external to the nonvolatile memory device via a second bus, the nonvolatile memory device comprising:

• a memory cell array configured to store data;
• a page buffer circuit configured to sense data from the memory cell array;
• an input/output register electrically connected to a data input/output pin;
• and
• a control circuit configured to, in response to a first command that is received from the external device, output a sensing status of first data and store the first data in the input/output register.

A method of operating a nonvolatile memory device, the method comprising:

• receiving a read command via a first bus, the read command being for reading first data from an external device that is external to the nonvolatile memory device;
• receiving a first command via the first bus, the first command being related to the first data;
• in response to the first command, outputting status information of a status register via the first bus;
• in response to the first command, storing the first data in an input/output register based on the status information;
• and
• in response to a select chip enable signal, outputting the first data stored in the input/output register via a second bus.