Using an add-on storage device for extending the storage capacity of a storage device in a host device

1. A method of data transfer to and from a storage device embedded in a host device, the storage device having a memory, a controller, a host interface connected to the host device and a storage device interface capable of being connected to an add-on memory, the method comprising:

if the storage device is not coupled to the add-on memory, storing in the storage device a file allocation table with entries beyond the storage capacity of the storage device, the file allocation table having entries for an initial address space of the storage device and entries for an extended address space, at least a subset of the entries for the extended address space are for locations in the add-on memory that will extend the capacity of the storage device at a later time, the entries in the file allocation table that are for the extended address space are marked as unavailable;

receiving a data transfer command from the host interface, the data transfer command specifying a memory address, wherein the memory has an address space;

determining if the specified memory address is beyond the address space of the memory;

if the specified memory address is beyond the address space of the memory and the add-on memory is coupled to the storage device embedded in the host device, routing the data transfer command to the storage device interface for access to the add-on memory, otherwise processing the data transfer command for access to the memory, wherein the address space of the memory and an address space of the add-on memory are addressed as one integral address space transparently to the host device; and

if the storage device is coupled to the add-on memory, storing the file allocation table with at least some of entries for the extended address space that are for locations in the add-on memory being marked as available;

the receiving, determining and routing are performed by the controller while embedded in the host device.

2. The method of claim 1 , further comprising:

coupling the add-on memory to the storage device within the host, and using the add-on memory without erasing content previously stored in the storage device and without reformatting the storage device,

3. The method of claim 1 , wherein:

the storage device is mounted under a battery cover for the host device.

4. The method of claim 3 , wherein the memory is formatted by a manufacturer of the storage device to enable transfer of content to and from the host device beyond the address space of the memory.

5. The method of claim 1 , wherein the routing involves translating the specified memory address via a defined logic.

6. The method of claim 1 , further comprising:

routing a response to the data transfer command, the response routed from the storage device interface to the host interface.

7. The method of claim 6 , wherein the routing involves translating the specified memory address via a pre-defined logic.

8. A storage device, comprising:

a host interface operative to connect with a host device;

a storage device interface operative to couple with an add-on memory;

a memory storing an allocation table having entries for an initial address space of the storage device and entries for an extended address space, prior to coupling the storage device to the add-on memory via the storage device interface at least a subset of the entries for the extended address space are for locations in the add-on memory that will extend the capacity of the storage device at a later time after coupling the add-on memory to the storage device and the entries for the extended address space that are for locations in the add-on memory are marked as unavailable, after coupling the add-on memory to the storage device at least a subset of the entries for the extended address space that are for locations in the add-on memory are marked as available; and

a controller configured to, when the host interface is connected to a host device and the add-on memory is coupled to the storage device:

receive a data transfer command from the host interface, the data transfer command specifying a memory address,

determine if the specified memory address is beyond the address space of the memory, and

if the memory address is beyond the address space of the memory, route the data transfer command to the storage device interface for access to the add-on memory, otherwise processing the data transfer command for access to the memory;

wherein the address space of the memory and an address space of the add-on memory are addressed as one integral address space transparently to the host device.

9. The storage device of claim 8 , wherein the memory is an embedded memory device and the add-on memory is a removable storage device capable of being connected to the host device.

10. The storage device of claim 8 , wherein the storage device is a memory card.

11. The storage device of claim 8 , wherein:

prior to coupling the storage device to the add-on memory via the storage device interface, the file allocation table stores entries beyond the storage capacity of the storage device.

12. The storage device of claim 11 , wherein if the add-on memory is present and coupled to the memory, entries associated with the extended address space are made available according to the address space of the add-on memory.

13. The storage device of claim 8 , wherein when the controller routes the data transfer command to the storage device interface, the controller translates the specified memory address via pre-defined logic.

14. The storage device of claim 8 , in which the controller is further configured to:

route a response to the data transfer command, the response routed from the storage device interface to the host interface.

15. The storage device of claim 14 , wherein when the controller routes the response, the controller translates the specified memory address via pre-defined logic.

16. The storage device of claim 8 , wherein the storage device interface and the host interface are of the same type.

17. The storage device of claim 8 , wherein either one or both of the host interface and storage device interface conform to an SD (secured digital) port.

18. The storage device of claim 8 , wherein either one or both of the host interface and storage device interface conform to an eMMC (embedded multi-media content) port.

19. The storage device of claim 8 , wherein the memory is non-volatile flash-based memory technology.