Abstract:
According to disclosed embodiments, a semiconductor memory is disclosed that includes a memory array connected to a number of registers by a transfer bus of reduced size. Reduction of transfer bus size can be achieved without a significant increase in data processing speed. According to one embodiment ( 300 ) a semiconductor memory can include a number of cell regions ( 302 - 0  and  302 - 1 ) arranged in a first direction. Sense amplifier banks ( 304 - 0  to  304 - 2 ) are connected to the cell regions ( 302 - 0  and  302 - 1 ) and a transfer bus ( 310 - 0/1 ) is disposed over the cell regions ( 302 - 0  and  302 - 1 ) in the first direction. The transfer bus ( 310 - 0/1 ) includes switching circuits ( 312 - 0  and  312 - 1 ) corresponding to each cell region ( 302 - 0  and  302 - 1 ). The switching circuits ( 312 - 0  and  312 - 1 ) can divide the transfer bus ( 310 - 0/1 ) into a number of transfer bus line portions ( 314 - 0/1, 316 - 0/1  and  318 - 0/1 ).

Description:
This application is a continuation of patent application Ser. No. 09/352,717 filed Jul. 13, 1999, abandoned. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to semiconductor memories, and more particularly to a semiconductor device having two memory portions that are connected by a transfer bus of reduced size. 
     BACKGROUND OF THE INVENTION 
     Many computer systems can include a main memory. In order to maintain reasonable costs in such computer systems, main memories are typically composed of dynamic random access memories (DRAMs). DRAMs can be fabricated in a variety of configurations and sizes. In the past, general purpose (asynchronous) DRAMs could provide sufficient speed at a low enough cost to be used in a main memory. 
     More recently, however, computer operating speeds have begun to outpace the speed of general purpose DRAMS. In particular, processor speeds have outpaced the data transfer rates of general purpose DRAMs. To alleviate the disparities in processor rates and general purpose DRAM data transfer rates, many systems have employed a substorage device situated between a main memory and a processor. Such substorage devices are typically referred to as “cache” memories. A cache memory is typically a high-speed memory device, such as a static RAM (SRAM) or an emitter coupled logic bipolar RAM (ECLRAM), to name just a few examples. A cache memory can be integrated into a processor, or may be provided external to the processor. 
     Another variation in memory devices combines DRAMs and high speed cache-type RAMs on the same device. Such combination devices have been utilized in computer workstations and some personal computers. Such devices can include a main storage formed from a DRAM and a cache memory formed from a SRAM. Both the DRAM and SRAM are formed on the same semiconductor substrate. Such devices have been referred to as cache DRAMs or CDRAMs. 
     CDRAMs can be arranged to transfer data between the DRAM and SRAM portions in a bidirectional fashion. When a memory is accessed, if the requested data location is in the SRAM portion, the access can be considered a cache “hit.” If a requested data location is not in the SRAM portion, the access can be considered a cache “miss.” The requested data can then be retrieved from the DRAM. A drawback to conventional CDRAMs is that cache misses can introduce some delay into a data transfer operation. 
     Another drawback to such CDRAMs is the number of external pins that are utilized in such devices (pin count). Because the DRAM portion and SRAM portion have their own respective address pins, the number of pins on a CDRAM can be much larger than those of a conventional DRAM. Therefore, a CDRAM device is not easily utilized with typical DRAM controllers. 
     Yet another problem associated with conventional CDRAMs is the amount of area that may be needed to realize a data transfer circuit. Because the area available for such circuits can be limited, the number of transfer bus lines between a DRAM and SRAM portion can also be limited. 
     Due to the above constraints, the number of data bits that can be transferred at the same time between a DRAM portion and a SRAM portion on a CDRAM can be limited. Further, many conventional CDRAM approaches avoid placing transfer lines in the same area as column select lines. As a result, the number of transfer lines can further be limited by the width of such available areas. As a general rule, the smaller the number of bits that can be transferred between DRAM and SRAM portions, the lower hit rate of the cache. One skilled in the art would recognize that lower cache hit rates leads to slower overall data access operations for a CDRAM. 
     The current applicant has previously proposed a “virtual channel” memory. In particular, a virtual channel synchronous DRAM (VCSDRAM) has been disclosed in Japanese Patent Publication No. Hei 11-86559 that can increase the access speed of a SDRAM. 
     The above-described VCSDRAM can include a memory array of DRAM cells arranged into rows and columns. In addition to the memory array, the VCSDRAM can include a register array having a number of rows and columns. The number of rows and/or columns in the register array can be some ratio of the number of rows and/or columns in the memory array. The register array can provide a cache function in the row and or column directions, and can include SRAM cells. 
     The above-described VCSDRAM can have a number of applications. One particular advantageous application of a VCSDRAM is the storing and/or displaying of video data. Data can be stored within a memory cell as picture elements (pixels). Pixel data can then be read out in a successive fashion from the same region of the memory array. The pixel data can be amplified by a sense amplifier group corresponding to the memory array region. Particular sense amplifiers can then be selected to transfer data to the channel register by way of a transfer bus. 
     Referring now to FIG. 6, a VCSDRAM, such as that referred to above, is illustrated in a block diagram. The VCSDRAM is designated by the general reference character  600 , and is shown to include two cell regions, designated as  602 - 0  and  602 - 1 . The cell regions ( 602 - 0  and  602 - 1 ) can include a number of memory cells connected to digit lines, one of which is shown as  604 . As just one arrangement, the digit lines can be connected to memory cells in a column-wise direction. 
     A number of sense amplifiers, one of which is shown as item  606 , are situated adjacent to both cell regions ( 602 - 0  and  602 - 1 ). Sense amplifier  606  (and those sense amplifiers within its group) can be considered “cornmon” to both cell regions ( 602 - 0  and  602 - 1 ). At the other end of cell region  602 - 0  is another group of sense amplifiers, one of which is shown as item  608 . Further, at the other end of cell region  602 - 1  is a third group of sense amplifiers, one of which is shown as item  610 . In the arrangement of FIG. 6, sense amplifier  608  (and those sense amplifiers within its group) is dedicated to cell region  602 - 0 , and sense amplifier  610  (and those sense amplifiers within its group) is dedicated to cell region  602 - 1 . 
     The VCSDRAM  600  further includes a number of registers  614 - 0  to  614 - 2  disposed at one end of the cell regions ( 602 - 0  and  602 - 1 ). The registers ( 614 - 0  to  614 - 2 ) can be connected to the various sense amplifier groups by transfer bus lines, shown as  616 - 00  to  616 - 21 . Connections between the sense amplifiers and their associated transfer bus lines ( 616 - 00  to  616 - 21 ) can be conventional in nature, and are not shown in particular in FIG.  6 . 
     For example, transfer bus lines  616 - 20 / 21  can transfer data from sense amplifier  606 ,  608  or  610  to channel register  614 - 2 . That is, one sense amplifier group can be activated, and thereby place data on the transfer bus lines ( 616 - 00  to  616 - 21 ) and into registers ( 614 - 0  to  614 - 2 ). Data stored in registers ( 614 - 0  to  614 - 2 ) can be transferred to external locations according to channel read and channel write commands. 
     In the arrangement of FIG. 6, signals SSU 1 , SSU 2 , SSM 1 , SSM 2 , SSD 1  and SSD 2  indicate sense amplifier selection signals. Sense amplifier selection signals can be applied to sense amplifier groups by way of select lines, shown as  618 - 00 / 01 ,  618 - 10 / 11 , and  618 - 20 / 21 . In the arrangement of FIG. 6, sense amplifier groups can be conceptualized as including “even” sense amplifiers that alternate with “odd” sense amplifiers. Accordingly, select signal SSU 1  can select even sense amplifiers from the group that includes sense amplifier  608 , and select signal SSU 2  can select odd sense amplifiers. Along these same lines, select signal SSM 1  can select even sense amplifiers and SSM 2  can select odd sense amplifiers from the group that includes sense amplifier  606 , and select signal SSD 1  can select even sense amplifiers and SSD 2  can select odd sense amplifiers from the group that includes sense amplifier  610 . 
     Referring once again to FIG. 6, when the SSU 1  signal is activated, sense amplifier  608  can place data on transfer lines  616 - 20 / 21 . However, if the SSU 2  signal is activated, the sense amplifier to the left of sense amplifier  608  can place data on transfer lines  616 - 20 / 21 . Data on transfer lines  616 - 20 / 21  can be stored in channel register  614 - 2 . 
     It can be understood from the above description that in the arrangement of FIG. 6, when a cell region (such as  602 - 0  or  602 - 1 ) is accessed, data from one of four sense amplifiers will be placed on a given transfer line. In particular, in FIG. 6, when cell region  602 - 0  is accessed, data will be placed on transfer lines  616 - 20 / 21  according to whether select signal SSU 1 , SSU 2 , SSM 1  or SSM 2  is activated. 
     A drawback to the arrangement of FIG. 6 is that a pair of transfer lines ( 616 - 00 / 01  to  616 - 20 / 21 ) is provided for every two sense amplifiers in a row. It may be difficult and/or inefficient to form transfer lines with such a periodicity (i.e., pitch). 
     Another drawback to the arrangement of FIG. 6 is that for speed and/or power purposes, the data signal carried on transfer lines ( 616 - 00  to  616 - 21 ) can have a relatively small amplitude. Consequently, to minimize disturbing such a data signal it may be necessary in some cases to employ shielding conductors  620 . Shielding conductors  620  can reduce “crosstalk” between adjacent transfer line pairs ( 616 - 00 / 01  to  616 - 20 / 21 ). Accordingly, the use of such shielding conductors can further increase line pitch, as three lines are provided for every two sense amplifiers in a row. 
     As semiconductor manufacturing processes advance, it can be possible to decrease device sizes, resulting in reductions in storage device (such as memory cells and registers) and sense amplifier size. However, it may not always be possible to reduce conductive line (“wire”) size, particularly if the conductive line is formed from a higher level of metallization. As a result, while device sizes decrease, structures that include a number of conductive lines may not scale down correspondingly. This may be particularly true for buses, such as a transfer bus in a memory device like a VCSDRAM. 
     It would be desirable to provide a semiconductor device that includes two memory portions (such as a DRAM and SRAM portion) joined by a transfer bus having a decreased number of transfer bus lines. It would also be desirable for such a reduced-bus size semiconductor device to maintain a relatively high data transfer rate. It would be further desirable for such a semiconductor device to be a VCSDRAM. 
     SUMMARY OF THE INVENTION 
     An object of the present invention to provide a semiconductor device having a first memory portion connected to a second memory portion with a transfer bus having a reduced number of bus lines. Even with such a reduced bus size, the semiconductor device can maintain a relatively high data processing speed for image processing, or the like. 
     To achieve the above-mentioned object, a semiconductor memory according to one embodiment of the present invention can include a memory cell array having a number of cell regions disposed in a first direction, sense amplifiers corresponding to each cell region, and a transfer bus extending in the first direction over the cell regions. The transfer bus can include a number switch circuits, each switch circuit corresponding to a cell region. The switch circuits can divide the transfer bus into a number of transfer bus portions. 
     In the above-described arrangement it can be possible to transfer data on multiple transfer bus portions created by dividing the transfer bus. In this way the efficiency of the transfer bus can be improved without increasing the overall number of transfer bus lines. Further, the number of registers (i.e., the size of second memory portion) can be increased. 
     In particular, one transfer bus (divided by a switch circuit) can be shared by channel registers. This can allow the number of registers to be doubled while maintaining essentially the same data processing speed. 
     It is understood that while the present invention may be advantageously employed in a virtual channel synchronous dynamic random access memory (VCSDRAM), the invention should not be construed as being limited to such a particular application. Further, the various general portions described, such as a transfer bus, register and memory cell region, should not be limited. Structures for other conventional semiconductor memories can be used for these portions. 
     In a preferred arrangement, channel registers are situated at both ends of a transfer bus. In this way, each channel register can transfer data to and from a memory cell via a transfer bus portion. 
     Also in a preferred arrangement, a transfer bus can include a transfer bus line divided into a number of transfer bus line portions. A sense amplifier group can be associated with each transfer bus line portion. Data can be placed on a transfer bus line portion by activating one sense amplifier of the corresponding sense amplifier group. 
     Furthermore, in a preferred arrangement, switching circuits are turned off before a memory cell in a corresponding memory cell array is selected. This operation can reduce interference between multiple memory cell arrays. 
     Furthermore, in a preferred arrangement, a group of sense amplifiers can be common to two memory cell arrays. The group of sense amplifiers can be situated between its corresponding arrays, reducing the space consumed by the group of sense amplifiers. 
     Furthermore, in a preferred arrangement, a switching circuit can have a number of switch banks, a memory array can have a number of array banks, and the channel registers can be arranged into a number of channel register portions. The switching circuit can be turned off in response to a number of commands. Two such commands include a prefetch instruction which can transfer data from a sense amplifier to a channel register, and a restore command that can transfer data from a channel register to a sense amplifier. In such an arrangement, data can be transferred from multiple array banks to corresponding multiple channel register portions over transfer bus portions created by the switch banks. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a semiconductor memory according to a first embodiment. 
     FIG. 2 is a circuit diagram of sense amplifier arrangement that may be used in the semiconductor memory of FIG.  1 . 
     FIG. 3 is a block diagram of a semiconductor memory according to a second embodiment. 
     FIG. 4 is a circuit diagram of sense amplifier arrangement that may be used in the semiconductor memory of FIG.  3 . 
     FIG  5  is a block diagram of a semiconductor memory according to a third embodiment. 
     FIG. 6 is a block diagram of a virtual channel synchronous dynamic random access memory (VCSDRAM). 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Various embodiments of the present invention will now be described with reference to a number of drawings. 
     FIG. 1 is a block diagram of a semiconductor memory according to a first embodiment. The first embodiment is designated by the general reference character  100  and is shown to include a cell region  102 , and the surrounding vicinity. A first sense amplifier bank  104 - 0  is situated on one side of cell region  102 , while a second sense amplifier bank  104 - 1  is situated on the other side of cell region  102 . 
     A number of channel registers  106 - 0  to  106 - 3  are also illustrated in FIG.  1 . The channel registers ( 106 - 0  to  106 - 3 ) are arranged into two groups, with a first group including channel registers  106 - 0  and  106 - 1  and a second group including channel registers  106 - 2  and  106 - 3 . The channel registers ( 106 - 0  to  106 - 3 ) are coupled to the cell region  102  by a data transfer bus  108 . 
     A data transfer bus  108  can include bus line pairs  110 - 00 / 01  and  110 - 10 / 11 . In the arrangement of FIG. 1, data is placed on bus line pairs ( 110 - 00 / 01  and  110 - 10 / 11 ) by activating one of every four sense amplifiers in a bank ( 104 - 0  and  104 - 1 ). That is, in each sense amplifier bank ( 104 - 0  and  104 - 1 ) there are four sense amplifiers for every bus line pair ( 110 - 00 / 01  and  110 - 10 / 11 ). While not set forth in detail in FIG. 1, the sense amplifiers can be connected to the bus line pairs by gate circuits or the like. Examples of such connections will be described with reference to FIGS. 2 and 4. 
     The sense amplifiers are labelled to identify particular groups of sense amplifiers within each bank ( 104 - 0  and  104 - 1 ). The sense amplifiers of bank  104 - 0  are labelled Sa 1  to Sa 4  and the sense amplifiers of bank  104 - 1  are labelled Sb 1  to Sb 4 . Each group of sense amplifiers can be associated with a corresponding transfer bus line ( 110 - 00 / 01  and  110 - 10 / 11 ). In the arrangement of FIG. 1, the sense amplifiers can be connected to digit lines, four of which are shown as Da 1 N, Da 1 T, Db 1 N and Db 1 T. The digit lines can be connected to columns of memory cells within memory cell region  102 . 
     A sense amplifier within a particular group can be selected by an associated sense amplifier select signal. In FIG. 1, the sense amplifiers Sa 1 -Sa 4  can-be selected by sense amplifier select signal SSa 1  to SSa 4 , respectively, and sense amplifiers Sb 1 -Sb 4  can be selected by sense amplifier select signal SSb 1  to SSb 4 , respectively. 
     Also included in FIG. 1 are switching circuits  112 - 0  and  112 - 1  connected to transfer bus line pairs  110 - 00 / 01  and  110 - 10 / 11  , respectively. Each switching circuit  112 - 0  and  112 - 1  can be conceptualized as being associated with cell region  102 . Further, each switching circuit  112 - 0  and  112 - 1  can be conceptualized as dividing its respective transfer bus line pair ( 110 - 00 / 01  and  110 - 10 / 11 ) in the vertical direction of FIG.  1 . As just one example, switching circuit  112 - 0  may have an “on” state and an “off” state. In the off state, switching circuit  112 - 0  can divide transfer bus line pair  110 - 00 / 01  into an upper bus line pair portion  114 - 00 / 01  and a lower bus line pair portion  116 - 00 / 01 . Transfer bus line pair  110 - 10 / 11  can be divided into an upper bus line pair portion  114 - 10 / 11  and a lower bus line pair portion  116 - 10 / 11  by switching circuit  112 - 1 . 
     Sense amplifiers from bank  104 - 0  can be connected to upper bus line pair portions ( 114 - 00 / 01  and  114 - 10 / 11 ) and sense amplifiers from bank  104 - 1  can be connected to lower bus line pair portions ( 116 - 00 / 01  and  116 - 10 / 11 ). In this way, the first embodiment  100  can transfer two sets of data values by dividing a set of transfer bus lines ( 110 - 00  to  110 - 11 ) with switching circuits ( 112 - 0  and  112 - 1 ). In this way, transfer bus lines ( 110 - 00  to  110 - 11 ) can be shared. 
     The switching circuits ( 112 - 0  and  112 - 1 ) are shown to receive a bus division signal SW. The switching circuits ( 112 - 0  and  112 - 1 ) can provide a high impedance path when turned off and a low impedance path when turned on. One of the many possible configuration for a switch circuit can include two transistors that are turned on and off according to the SW signals. Another of the possible configurations can include a transfer gate having complementary devices, such as two n-channel transistors and two p-channel transistors. 
     It is noted that the block diagram of FIG. 1 can be conceptualized as including circuit cell portion that is logically arranged into a “bank.” The bank structure of FIG. 1 is indicated by the reference character  118 . 
     Referring now to FIG. 2, a circuit diagram is set forth illustrating a sense amplifier arrangement that may be used in the first embodiment of FIG.  1 . FIG. 2 can be considered to correspond to the four sense amplifiers Sal to Sa 4  that are associated with transfer bus line pair  110 - 00 / 11 . 
     The arrangement of FIG. 2 is designated by the general reference character  200  and is shown to include sense amplifiers  202 - 1  to  202 - 4 , that can be conceptualized as corresponding to sense amplifiers Sa 1  to Sa 4 . Each sense amplifier ( 202 - 1  to  202 - 4 ) can receive and amplify input signals on corresponding digit line pairs  204 - 10 / 11  to  204 - 40 / 41 . 
     In FIG. 2, each sense amplifier ( 202 - 1  to  202 - 4 ) can include a “flip-flop” section  206 - 1  to  206 - 4  and a transfer section  208 - 0  to  208 - 4 . Each “flip-flop” section  206 - 1  to  206 - 4  can include two p-channel metal(conductor)-oxide(insulator)-semiconductor (PMOS) transistors (P 200 /P 202 ) and two n-channel MOS (NMOS) transistors (N 200 /N 202 ). The flip-flop sections ( 206 - 1  to  206 - 4 ) can amplify signals on the digit line pairs ( 204 - 10 / 11  to  204 - 40 / 41 ). Each transfer section ( 208 - 1  to  208 - 4 ) can include two NMOS transistors N 204 /N 206 . Transfer sections  208 - 1  to  208 - 4  can be turned on by sense amplifier selection signals SSa 1  to SSa 4 , respectively. When turned on, a transfer section ( 208 - 1  to  208 - 4 ) can couple its associated digit line pair ( 204 - 10 / 11  to  204 - 40 / 41 ) to a transfer bus line pair  210 - 0 / 1 . 
     The sense amplifiers ( 202 - 1  to  2024 ) can be commonly activated by a first enable signal SAP and a second enable signal SAN. One skilled in the art would recognize that the SAN and SAP signals can supply an activating potential that enables the amplifying function of the sense amplifiers. 
     Referring now to FIG. 3, a block diagram is set forth of a semiconductor memory according to a second embodiment. The second embodiment is designated by the general reference character  300 . The second embodiment  300  can differ from the first embodiment  100  in that it sets forth a more than one cell region and a “common” sense amplifier bank. A common sense amplifier bank can be a sense amplifier bank that is coupled to more than one cell region. 
     The block diagram of FIG. 3 is shown to include cell regions  302 - 0  and  302 - 1 , an upper sense amplifier bank  304 - 0 , a middle common sense amplifier bank  304 - 1 , and a lower sense amplifier bank  304 - 2 , and channel registers  306 - 0  and  306 - 1 . In the view of FIG. 3, channel registers ( 306 - 0  and  306 - 1 ) are coupled to the cell regions ( 302 - 0  and  302 - 1 ) by a data transfer bus line pair  310 - 0 / 1 . The data transfer bus lines  310 - 0 / 1  can be divided by the operation of switching circuits  312 - 0  to  312 - 1 . In the arrangement of FIG. 3, the switching circuits  312 - 0  to  312 - 1  can divide the data transfer bus lines  310 - 0 / 1  into an upper transfer bus portion  314 - 0 / 1 , a middle transfer bus portion  316 - 0 / 1  and a lower transfer bus portion  318 - 0 / 1 . Switching circuits  312 - 0  and  312 - 1  are controlled by bus division signals SSW 1  and SSW 2 , respectively. 
     The sense amplifiers of common sense amplifier bank  304 - 1  are shared by cell regions  302 - 0  and  302 - 1 . Within the sense amplifier banks ( 304 - 0  to  304 - 2 ), the sense amplifiers can be conceptualized as being arranged into groups that are coupled to the data transfer bus lines  310 - 0 / 1 . The sense amplifier group of bank  304 - 0  are labelled Sa 1  to Sa 4 , the sense amplifier group of bank  304 - 1  are labelled Ss 1  to Ss 2 , and the sense amplifier group of bank  304 - 2  are labelled Sb 1  to Sb 4 . A sense amplifier within each group can be selected according to sense amplifier select signals. In particular, sense amplifiers Sa 1  to Sa 4  can be selected by sense amplifier select signals SSa 1  to SSa 4 , respectively, sense amplifiers Ss 1  to Ss 4  can be selected by sense amplifier select signals SSs 1  to SSs 4 , respectively, and sense amplifiers Sb 1  to Sb 4  can be selected by sense amplifier select signals SSb 1  to SSb 4 , respectively. 
     Data provided by a selected sense amplifier can be connected to a data transfer bus line pair by wiring structures. In particular, the sense amplifiers of banks  304 - 0  to  304 - 2  can be coupled to the data transfer bus line pair  310 - 0 / 1  by wiring line pairs  320 - 00 / 01  to  320 - 20 / 21 , respectively. 
     An example of the operation of the second embodiment  300  will now be described. The operation includes the selection of a word line  322  within cell region  302 - 0 . Bus division signals SSW 1  and SSW 2  can be turned on, and the transfer bus lines  310 - 0  and  310 - 1  set to a predetermined potential. Corresponding to the selection of word line  322 , bus division signal SSW 1  is turned off. Bus division signal SSW 2  can remain on, resulting in transfer bus lines  310 - 0  and  310 - 1  being divided into two portions, one portion including upper portion  314 - 0 / 1  the other portion including middle and lower portions  316 - 0 / 1  and  318 - 0 / 1 . 
     The operation can proceed with the cell region  302 - 0  outputting cell data onto digit lines, one of which is shown as item  324 . Sense amplifiers, selected by sense amplifier selection signals, can amplify the cell data on the digit lines. In the described example, with word line  322  selected, a sense amplifier in sense amplifier bank  304 - 0  can be selected according to sense amplifier selection signals SSa 1  to SSa 4 , and/or a sense amplifier in sense amplifier bank  304 - 1  can be selected according to sense amplifier selection signals SSs 1  to SSs 4 . 
     Data from the selected sense amplifier can be connected to a portion of the transfer bus lines  310 - 0  and  310 - 1 . For example, if sense amplifier Sa 1  is selected, data from the sense amplifier can be connected to an upper transfer line portion (formed by  314 - 0 / 1 ) through wiring line pair  320 - 00 / 01 . If common sense amplifier Ss 1  is selected, data from the sense amplifier can be connected to a lower transfer line portion (formed by  316 - 0 / 1  and  318 - 0 / 1 ) through wiring line pair  320 - 10 / 11 . 
     When a word line  322  in cell region  302 - 0  is selected, sense amplifier select signals SSb 1  to SSb 4  can be deselected to avoid applying data from two cell regions ( 302 - 0  and  302 - 1 ) to common transfer line portions ( 316 - 0 / 1  and  318 - 0 / 1 ). 
     It is noted that the block diagram of FIG. 3 can be conceptualized as including a circuit cell portion that is logically arranged into a “bank.” The bank structure of FIG. 3 is indicated by the reference character  326 , and is shown to include multiple cell portions. 
     As shown by FIG. 3, the second embodiment can include multiple cell regions that can be accessed by a dividable transfer bus and a bank of common sense amplifiers. 
     Referring now to FIG. 4, a circuit diagram is set forth illustrating a sense amplifier arrangement that may be used in the second embodiment of FIG.  3 . FIG. 4 can be considered to correspond to the four common sense amplifiers Ss 1  to Ss 4  set forth in FIG.  3 . 
     The arrangement of FIG. 4 is designated by the general reference character  400  and is shown to include sense amplifiers  402 - 1  to  402 - 4 , that can be conceptualized as corresponding to sense amplifiers Ss 1  to Ss 4 . Each sense amplifier ( 402 - 1  to  402 - 4 ) can receive and amplify input signals on digit line pairs  404 - 10 / 11  to  404 - 40 / 41  associated with one cell region, and digit line pairs  404 - 50 / 51  to  404 - 80 / 81  associated with another cell region. 
     Each sense amplifier ( 402 - 1  to  402 - 4 ) can include a “flip-flop” section  406 - 1  to  406 - 4  and a transfer section  408 - 1  to  408 - 4 . Each “flip-flop” section  406 - 1  to  406 - 4  can include two PMOS transistors (P 400 /P 402 ) and two NMOS transistors (N 400 /N 402 ). The flip-flop sections ( 406 - 1  to  406 - 4 ) can amplify signals on the digit line pairs ( 404 - 10 / 11  to  404 - 40 / 41  or  404 - 50 / 51  to  404 - 80 / 81 ). The sense amplifiers ( 402 - 1  to  402 - 4 ) can be commonly activated by sense amplifier select signals SAN and SAP. 
     Each transfer section ( 408 - 1  to  408 - 4 ) can include two NMOS transistors N 404 /N 406 . Transfer sections  408 - 1  to  408 - 4  can be turned on by sense amplifier selection signals SSsl to SSs 4 , respectively. When turned on, a transfer section ( 408 - 1  to  408 - 4 ) can couple its associated digit line pair ( 404 - 10 / 11  to  404 - 80 / 81 ) to a transfer bus line pair  410 - 0 / 1 . 
     The arrangement of FIG. 4 further includes first transfer gates  412 - 01  to  412 - 04  and second transfer gates  412 - 11  to  412 - 14 . First transfer gates ( 412 - 01  to  412 - 04 ) can connect digit line pairs  404 - 50 / 51  to  404 - 80 / 81  to sense amplifiers  402 - 1  to  402 - 4 . First transfer gates ( 412 - 01  to  412 - 04 ) can include two NMOS transistors N 408  and N 410  that are controlled by a transfer gate signal TG 1 . Second transfer gates ( 412 - 11  to  412 - 14 ) can connect digit line pairs  404 - 10 / 11  to  404 - 40 / 41  to sense amplifiers  402 - 1  to  402 - 4 . Second transfer gates ( 412 - 11  to  412 - 14 ) can include two NMOS transistors N 412  and N 414  that are controlled by a transfer gate signal TG 2 . 
     FIG. 5 is a block diagram of a semiconductor memory device according to a third embodiment. The third embodiment is designated by the general reference character  500 , and can differ from the first and second embodiments ( 100  and  300 ) in that it includes a plurality of banks. 
     Referring now to FIG. 5, the third embodiment  500  is shown to include a first register group  502 - 0 , a second register group  502 - 1 , a first bank (BANK A)  504 - 0 , and a second bank (BANK B)  504 - 1 . A data transfer bus  506  can connect first and second banks ( 504 - 0  and  504 - 1 ) to first and second register groups ( 502 - 0  and  502 - 1 ). 
     The banks (such as  504 - 0  and  504 - 1 ) of the third embodiment  500 , as just two examples, can have structures like those of the first embodiment bank  118  and/or the second embodiment bank  326 . 
     It is understood that in one particular arrangement, that the data transfer bus  506  can be separated into portions according to switching circuits within the banks. In the arrangement of FIG. 5, switching circuits within the first bank  504 - 0  can be controlled by bus division signals SSW 1 A and SSW 1 B. Switching circuits within the second bank  504 - 1  can be controlled by bus division signals SSW 2 A and SSW 2 B. 
     In particular, switching circuits can divide the data transfer bus according to a prefetch or restore signal received from a memory controller. A prefetch or restore signal can direct data transfers between channel registers (within register groups  502 - 0  and  502 - 1 ) and sense amplifiers (within banks  504 - 0  and  504 - 1 ). 
     Operations for one version of the third embodiment will now be described in conjunction with FIGS. 3 and 5. For the purposes of this description it is assumed that the third embodiment  500  includes a bank having the structure of the second embodiment  326 . 
     When a memory cell is not selected, switching circuits (such as  312 - 0  and  312 - 1 ) are turned on, and the data transfer bus  506  is set to a predetermined potential. A word line can be selected (such as  322 ) and data can be amplified by sense amplifier banks ( 304 - 0  and  304 - 1 ) situated at opposing ends of the cell region  302 - 0  containing the selected word line  322 . Amplification of sense amplifier data can be accomplished by sense amplifier enable signals such as SAP and SAN. 
     The bus division signals SSW 1 A, SSW 1 B, SSW 2 A and SSW 2 B can be deselected at this time, dividing the transfer bus  506  into a number of sections. Further, sense amplifier select signals (such as SSs 1  to SSs 4 ) are also deselected. 
     A control signal can then be received from an external controller to initiate a data transfer between a bank ( 504 - 0  and  504 - 1 ) and the register groups ( 502 - 0  and  502 - 1 ). In the event a word line has been selected within first bank  504 - 0 , bus division signal SSW 1 A can be turned off, while bus division signal SSW 1 B can be turned on. Further, the bus division signals associated with the second bank  504 - 1  (SSW 2 A and SSW 2 B) can be turned on. In this way, the data transfer bus  506  can be divided into one portion coupled to a first register group  502 - 0  and another portion coupled to a second register group  502 - 1 . 
     In this way, memory cell data can be accessed in a bank ( 504 - 0  and  504 - 1 ), and then transferred via a divided data transfer bus  506  to first and second register groups ( 502 - 0  and  502 - 1 ). 
     It is noted that in the cases of the first and second embodiments ( 100  and  300 ), the switching circuits (such as  112 - 0  and  112 - 1  and  312 - 0  and  312 - 1 ) can divide a transfer bus ( 110 - 00  to  110 - 11  and  310 - 0 / 310 - 1 ) in response to the selection of a word line. 
     The third embodiment  500  can differ from the first and second embodiments ( 100  and  300 ) in that the data transfer bus  506  can be divided by switching circuits in response to a prefetch or restore signal that can initiate a data transfer between register groups ( 502 - 0  and  502 - 1 ) and banks ( 504 - 0  and  504 - 1 ). For example, if an arrangement such as that of FIG. 5 includes data transfer bus division according to word line selection, word lines may be selected in both banks at the same time. In such a case, the data transfer bus could be divided into three portions, preventing the desired data from being transferred to the register groups ( 502 - 0  and  502 - 1 ). 
     Accordingly, by dividing the data transfer bus  506  in response to a prefetch or restore signal, a switching circuits within one bank can be turned off, while those in another bank can be turned on. For example, if a transfer is to occur between the first bank  504 - 0  and register groups  504 - 0  and  504 - 1 , a set of switching circuits within first bank  504 - 0  can be turned off by deselecting the SSW 1 A or SSW 1 B signal. At the same time the SSW 2 A and SSW 2 B signals can be selected. In this arrangement, data in the first bank  504 - 0  can be transferred to both channel registers ( 502 - 0  and  502 - 1 ). 
     It is understood that while various descriptions have described accesses to the first bank  504 - 0 , similar accesses can occur to the second bank  504 - 1 . 
     As described in the various embodiments, a semiconductor memory according the present invention can advantageously reduce the number of transfer bus lines while maintaining data transfer speeds of a virtual channel memory. Such a semiconductor memory device may be advantageously employed in image processing applications. 
     It is also noted that while the various arrangements have illustrated sense amplifier arrangements having a ratio of 4:1 with respect to corresponding channel registers, such a configuration should not be construed as limiting the invention thereto. 
     The particular arrangement of memory device components can also be subject to variation. As but one example, while the switching circuits ( 112 - 0  and  112 - 1 ) of FIG. 1 are illustrated as being situated between sense amplifier bank  104 - 1  and cell region  102 , one or all of such switching circuits ( 112 - 0  and  112 - 1 ) can be situated at various locations between sense amplifier banks  104 - 0  and  104 - 1 . 
     It is further understood that while the various figures have illustrated arrangements that include a limited number of data transfer lines, many such lines can be arranged in parallel to form a larger bus structure. 
     The present invention has been described in conjunction with a number of embodiments. However, a semiconductor memory of the present invention should not be construed as being restricted to such embodiments. Various modifications to the disclosed embodiments are included in the range of the present invention. As just one example, a semiconductor memory of the present invention is not limited to a virtual channel memory, but can also be employed in a general-purpose memory. 
     It is thus understood that while various particular embodiments set forth herein have been described in detail, the present invention could be subject to various changes, substitutions, and alterations without departing from the spirit and scope of the invention. Accordingly, the present invention is intended to be limited only as defined by the appended claims.