Buffer management device, buffer management method, and storage device

A storage device comprising:

• a connector configured to be connectable to a host device;
• a buffer memory configured to manage a storage area in a credit unit representing a predetermined data size and to temporarily store data transferred from the host device;
• a storage medium where the data temporarily stored in the buffer memory is to be written;
• a current-credit retaining module configured to retain number of credits currently available for the buffer memory as a current credit value;
• a reserved-credit retaining module;
• a transfer controller configured to register number of credits necessary to temporarily store the data in the reserved-credit retaining module as a reserved credit value prior to transfer of the data from the host device to the buffer memory;
• and
• a subtractor configured to subtract the reserved credit value registered in the reserved-credit retaining module from the current credit value retained by the current-credit retaining module and to output a subtraction result as an available credit value.

A buffer management method for managing a buffer memory configured to manage a storage area in a credit unit representing a predetermined data size and to temporarily store data transferred from an external device, the buffer management method comprising:

• retaining number of credits currently available for the buffer memory as a current credit value in a current-credit retaining module;
• registering number of credits necessary to temporarily store the data as a reserved credit value in a reserved-credit retaining module prior to transfer of the data to the buffer memory;
• and
• subtracting the reserved credit value registered in the reserved-credit retaining module from the current credit value retained by the current-credit retaining module and outputting a subtraction result as an available credit value.