the following discussion is presented to enable a person skilled in the art to make and use the invention . various modifications to the embodiments will be readily apparent to those skilled in the art , and the generic principles herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention . thus , the present invention is not intended to be limited to the embodiments shown , but is to be accorded the widest scope consistent with the principles and features disclosed herein . fig2 shows a storage system 20 , according to a first embodiment of the present invention , for an electronic device 27 . the storage system 20 comprises a controller 21 , at least one embedded storage device 23 , and at least one removable memory 24 . the embedded storage device 23 is connected to the electronic device 27 in a non - removable way . in particular , the embedded storage device 23 and the controller 21 are provided in a same chip 22 , represented schematically in fig2 by a dashed rectangle . inside the chip 22 , the embedded storage device 23 and the controller 21 occupy two physically distinct regions . the chip 22 ( see also fig3 ) can be housed in a package 25 , for example of a ball - grid - array ( bga ) type , and then soldered to a printed circuit 26 . the removable storage device 24 , for example a memory card , is instead removable from the electronic device 27 , and , in a known way , may be housed in a purposely provided slot 28 . the slot 28 has , inside , appropriate electrical contacts designed to interface with corresponding electrical contacts carried by the removable storage device 24 . conductive tracks 29 provided on the printed circuit 26 connect the removable storage device 24 , when housed in the slot 28 , to the controller 21 . the storage system 20 further comprises connections 30 , designed to connect the controller 21 to other parts ( not shown ) of the electronic device 27 . in greater detail , the controller 21 comprises a microprocessor 31 , which supervises operation of the controller 21 , and a single interface 33 , which communicates with the microprocessor 31 through an internal data bus 32 . it should be emphasized that the controller 21 is not equipped with a data - management function , and a single interface 33 operates for the embedded storage device 23 and the removable storage device 24 . according to one embodiment of the invention , the embedded storage device 23 and the removable storage device 24 have a similar architecture , and in particular are both provided with an integrated data - management function . in detail , the embedded storage device 23 and the removable storage device 24 comprise an interface 35 , a data manager 36 , and a memory 37 , constituted by an addressable array of memory cells , for example of a nand flash type ( in this case the data manager 36 implements the ftl ). in particular ( fig4 ), the data manager 36 comprises a microprocessor 38 provided with an integrated memory 39 ( either rom or ram ), which contains a firmware ( or integrated software ) programmed so as to obtain management of the data stored in the memory 37 . the interface 35 , the data manager 36 , and the memory 37 of the embedded storage device 23 are integrated in the chip 22 ; in particular , they are provided within the region of the chip 22 dedicated to the embedded storage device 23 . the storage system 20 further comprises an external data bus 40 , which connects the embedded storage device 23 and the removable storage device 24 , in particular the respective interfaces 35 , to the interface 33 of the controller 21 . positioning the data manager 36 within the embedded storage device 23 allows the controller 21 not to depend upon the physical structure of the embedded storage device 23 and removable storage device 24 . in particular , the controller 21 only needs to know the communication protocol used on the external data bus 40 , and it does not have to know the physical structure of the storage devices . therefore , the interface 33 within the controller 21 is just one , irrespective of the type and number of storage devices to which the controller 21 can be connected . basically , the external data bus 40 carries only generic input and output signals and control signals so that the controller 21 could be a generic input / output controller instead of a dedicated ( or application - specific ) controller . the external data bus 40 connected to the interface 33 of the controller 21 and to the interfaces 35 of the embedded and removable storage devices 23 , 24 can use any protocol of a known type , for example an mmc ( multimediacard ™) interface protocol , or an spi ( serial peripheral interface ) interface protocol or a usb ( universal serial bus ) interface protocol . in particular , any desired number of storage devices , whether embedded or removable , can be connected to the external data bus 40 according to the protocol used . according to a second embodiment of the present invention , illustrated in fig5 , the controller 21 and the embedded storage device 23 are formed in two distinct chips , illustrated by dashed rectangles designated , respectively , with the reference numbers 41 and 42 . the chips 41 and 42 can be both soldered to the pcb 26 and connected by conductive tracks , or can for example be stacked within a same package , for example a bga package , using the stacked - chip technique . in particular , the division of the controller 21 and of the embedded storage device 23 into two distinct chips enables a greater modularity and flexibility of the storage system 20 , since the storage density may be varied more easily . the disadvantage of a solution of this sort may be represented by the higher production costs . fig6 to 8 show , respectively , a third , a fourth and a fifth embodiment of the present invention , which differ simply as regards the implementation of the embedded storage device 23 . in detail , in the third embodiment ( fig6 ) the embedded storage device 23 is formed in two distinct chips 44 , 45 , one of which , for example the chip 44 , integrates the interface 35 , and the other , in the example the chip 45 , integrates both the data manager 36 and the memory 37 . advantageously , in order to reduce overall dimensions , the two chips 44 , 45 can be housed in a same package with the stacked - chip technique . according to the fourth embodiment ( fig7 ), the embedded storage device 23 is once again made in two distinct chips 47 , 48 . unlike the third embodiment , one of the chips , for example the chip 47 , integrates the interface 35 and the data manager 36 , while the other chip , in the example the chip 48 , integrates the memory 37 . according to the fifth embodiment ( fig8 ), the embedded storage device 23 is formed in three distinct chips 50 , 51 , 52 , which integrate the interface 35 , the data manager 36 , and the memory 37 , respectively . according to a further embodiment of the present invention ( see fig9 ), the storage system 20 , implemented according to any of the embodiments described previously , may further comprise a plurality of additional storage devices 60 , connected to the embedded storage device 23 and to the removable storage device 24 to increase their respective storage density , in a modular way . in particular , the additional storage devices 60 are formed by a simple storage element ( for example , an addressable array of cells of a nand flash type ) and are not provided with advanced data - management functions . the additional storage devices 60 are connected to the data manager 36 of the embedded storage device 23 and of the removable storage device 24 via a respective connection bus 62 . in this case , the embedded storage device 23 and the removable storage device 24 have a master function , because they have an integrated data - management function , while the additional storage devices 60 have a slave function , since they are managed by the data manager 36 of the respective embedded storage device 23 or removable storage device 24 . the additional memories ( slaves ) 60 that are provided for expanding the removable memory 24 must be in the same box as the removable memory 24 , in a different chip or in a different package . depending on the embodiment of the storage system 20 , the additional storage devices 60 connected to the embedded storage device 23 can be integrated within the chip 22 ( as illustrated in fig9 ), or each additional storage device 60 may be provided in a distinct chip . in the latter case , each additional storage device 60 may have a distinct package and be connected outside the master storage device , or alternatively , the various chips of the additional storage devices 60 can be stacked on the chip of the master storage device inside a same package . thereby , the storage system 20 is extremely modular and any desired number of additional storage devices 60 can be connected to the embedded and removable storage devices 23 , 24 so as to expand the corresponding storage density as desired . the advantages of the described embodiments of the present invention are evident from the above . in particular , the described storage system enables a simplification of the controller of the storage system , which does not perform a data management function , thus can be a controller of a general - purpose type , and hence a low - cost one . moreover , the controller has a single interface for all the different storage devices comprised in the storage system , which are all connected to the same data bus . in particular , in this way there is no need to replace the controller in the case where new types of storage devices are used . the storage system is moreover optimized since each storage device , whether embedded or removable , has a data manager and an interface optimized for the specific use of the storage device . finally , the storage system is extremely modular and enables addition of any desired number of additional storage devices to increase the storage density of the system . it is clear that modifications and variations may be made to what has been described and illustrated herein , without thereby departing from the scope of the present invention , as defined in the attached claims . in particular , it is evident that the storage system is not tied to the use of a particular type of memory ( flash memories of a nor type , or any other type of electrically writeable and erasable non - volatile memory , could for example be used instead of flash memories of a nand type ) or of a particular production technique . storage systems according to the described embodiments of the present invention in fig2 - 9 can be utilized in a variety of different types of electronic systems , such as cellular phones , digital cameras , mp3 and other types of audio and video players , personal digital assistants ( pdas ), and so on .