Embedded multimedia card (eMMC), host controlling eMMC, and method operating eMMC system

An embedded multimedia card (eMMC) system comprising:

• an eMMC comprising flash memory and an extended card specific data (CSD) register (“EXT_CSD register”) that stores information including maximum operating frequency information for the eMMC;
• and
• a host that controls operation of the eMMC and comprises:
• a clock generator that generates a clock provided to the eMMC;
• and
• a host controller that generates a maximum operating frequency control signal applied to the clock generator to determine a frequency of the clock,
• wherein the host controller is configured to send a SEND_EXT_CSD command to the eMMC and receive the maximum operating frequency information from the eMMC in response to the SEND_EXT_CSD command, and
• the maximum operating frequency control signal is generated in accordance with the maximum operating frequency information.

A method for operating an eMMC system including an embedded multimedia card (eMMC) and a host, the method comprising:

• providing a clock having a first frequency from the host to the eMMC;
• communicating a SEND_EXT_CSD command from the host to the eMMC;
• in response to the SEND_EXT_CSD command, reading information data from an extended card specific data (CSD) register (“EXT_CSD register”) disposed in the eMMC and communicating the information data to the host;
• and
• changing the frequency of the clock from the first frequency to a second frequency different from the first frequency and operating the flash memory in response to the clock having the second frequency,
• wherein the EXT_CSD register arranges the eMMC data according to a least one data field, and the at least one data field includes a VENDOR_SPECIFIC_FIELD field that stores data defining the maximum operating frequency for the clock.

A method of operating an eMMC system including an embedded multimedia card (eMMC) and a host, the method comprising:

• providing a clock having a first frequency from the host to the eMMC;
• communicating a SEND_EXT_CSD command from the host to the eMMC;
• in response to the SEND_EXT_CSD command, reading information data from an extended card specific data (CSD) register (“EXT_CSD register”) disposed in the eMMC and communicating the information data to the host;
• changing the frequency of the clock from the first frequency to a second frequency different from the first frequency;
• communicating a SWITCH command from the host to the eMMC;
• and
• changing timing interface between the eMMC and the host in response to the SWITCH command from a first timing interface to a second timing interface.