Memory controller, data storage device, and memory control method

A memory controller for controlling a first memory and a second memory, the first memory being configured as a non-volatile memory to which data is written by writing operation in which data is read on a page basis consisting of a plurality of sectors, a sector corresponding to writing data among the data being read is overwritten by the writing data, and then data is written on the page basis, and the second memory being configured as a non-volatile random access memory that allows faster data writing than the first memory, the memory controller comprising:

• a writing controller configured to control the first and second memories, upon input of the writing data and a writing request signal requesting writing of the writing data, such that the writing data being input is written to the first memory by the writing operation when a data utilization rate obtained if the writing data is written to the first memory is equal to or higher than a first rate, wherein the data utilization rate indicates a rate of a sector size used for storing the writing data based on a storage area having a predetermined size;
• and such that the writing data being input is stored in the second memory when the data utilization rate is lower than the first rate;
• and
• a data transfer controller configured to execute data transfer control that controls the first and second memories, with an empty space in the second memory being less than a predetermined amount, such that, at least on a necessary condition that data stored in the second memory is infrequently-rewritten data with a low rewritten frequency, the infrequently-rewritten data is read from the second memory to be written to the first memory by the writing operation,
• wherein the data transfer controller is configured to execute the data transfer control, with the empty space in the second memory being less than the predetermined amount, at least on necessary conditions that the data stored in the second memory is the infrequently-rewritten data and the data utilization rate obtained if the infrequently-rewritten data is written to the first memory is equal to or higher than a second rate, the second rate being lower the first rate.