Abstract:
Disclosed is data processing carried out by an SIMD (Single Instruction stream/Multiple Data stream) parallel processor. When the piece count of pixel data increases, another data processing apparatus is newly added to an existing data processing apparatus. Early M pieces of pixel data of an input signal is processed by the existing data processing apparatus whereas later M pieces of pixel data of the input signal is processed by the other data processing apparatus. An input pointer generating circuit employed in the other data processing apparatus is used to prevent the early M pieces of pixel data from being supplied to the other data processing apparatus by delaying the generation of an input pointer. A select signal generating circuit outputs a select signal to a selector for properly selecting either results of processing output by an output SAM unit employed in the existing data processing apparatus or results of processing output by an output SAM unit employed in the other data processing apparatus.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a data processing system and a data processing method adopted in the data processing system, and particularly to a data processing system and a data processing method adopted in the data processing system which are capable of keeping up with a case in which the piece count of pixel data to be processed increases by delaying the operating timing of input and output units employed in the data processing system. 
     As a related art data processing system, there is known a processor called an SVP (Serial Video Processor) described in Section 3.1 on Page 17 of the IEEE 1990 Custom Integrated Circuits Conference. Composed of 1,024 processors integrated in a single chip, the SVP is a processor for carrying out real time digital processing on a video signal. The SVP has an SIMD (Single Instruction stream/Multiple Data stream) structure which allows pixel data on a horizontal scanning line to be processed concurrently. SIMD is the name of one of data processing methods adopted by a computer whereby data of different kinds is processed concurrently as if the data pertained to one job. 
     FIG. 1 is a block diagram showing a typical configuration of an SIMD control parallel processor. As shown in the figure, the SIMD control parallel processor includes a program control apparatus  17 , an input SAM (Serial Access Memory) unit  11 , a data memory unit  12 , a processing circuit unit  13  and an output SAM unit  14 . 
     The input SAM unit  11 , the data memory unit  12 , the processing circuit unit  13  and the output SAM unit  14  constitute a group of parallel processor elements  15  arranged in a linear array. The processor elements  15  are controlled in a state being interlocked with each other in accordance with a program of the program control apparatus  17 , that is, subjected to the SIMD control. The program control apparatus  17  includes a program memory for storing the program in advance and a sequence control circuit for carrying on the program. The program control apparatus  17  generates a variety of control signals in accordance with the program in order to control a variety of circuits. 
     It should be noted that the input SAM unit  11 , the data memory unit  12 , and the output SAM unit  14  are each implemented as a memory, detailed explanation of which is omitted. In an apparatus shown in FIG. 1, row address decoders for these memories are included in the program control apparatus  17 . 
     One processor element  15  is represented by a hatched block in FIG. 1. A plurality of processor elements  15  are arranged in parallel, that is, in the horizontal direction of the figure. That is to say, the processor element  15  indicated by the hatch block includes components of one processor. 
     Next, the operation of the linear array parallel processor for carrying out video processing shown in FIG. 1 will be described. 
     Input data, strictly speaking, video data of one pixel, is supplied to the input SAM unit  11  in accordance with a control signal output by the program control apparatus  17 . The processor elements  15  from the leftmost one to the rightmost one shown in the figure sequentially process the data. That is to say, pieces of input data are supplied sequentially to input SAM cells of the input SAM unit  11  from the leftmost one to the rightmost one shown in the figure. 
     Since the number of the processor elements  15  is at least equal to the pixel count H in one horizontal scanning period of a video signal, pixel data of one horizontal scanning period of a video signal can be accommodated in the input SAM unit  11 . The operation to supply input data is repeated for each horizontal scanning period. 
     Each time data of one horizontal scanning period of a video signal is accumulated in the input SAM unit  11  as described above, the program control apparatus  17  carries out processing by executing SIMD control on the input SAM unit  11 , the data memory unit  12 , the processing circuit unit  13  and the output SAM unit  14  in accordance with the program as described below. In addition, the SIMD control causes the following operations to be executed in all the processor elements  15  concurrently in the same way. 
     The input data of one horizontal scanning period of a video signal accumulated in the input SAM unit  11  is, if necessary, transferred from the input SAM unit  11  to the data memory unit  12  during the next horizontal scanning fly-back line period to be used in the subsequent processing. 
     In a transfer of data from the input SAM unit  11  to the data memory unit  12 , the program control apparatus  17  makes an access to data of a predetermined bit count in the input SAM unit  11  selected by an input SAM read signal, and then outputs a memory access signal to write the data into a predetermined memory cell of the data memory unit  12 . 
     Next, the program control apparatus  17  supplies data stored in the data memory unit  12  of each processor element  15  to the processing circuit unit  13  of the processor element  15  in accordance with the program and lets the processing circuit unit  13  carry out arithmetic and logic processing on the data supplied thereto. Results of processing are then written at a predetermined address of the data memory unit  12 . 
     FIG. 2 is a block diagram showing a typical configuration of the processing circuit unit  13 . Pieces of data from the data memory unit  12  are supplied to a register  84  by way of a selector  80 , a register  85  by way of a selector  81  and a register  86  by way of a selector  82 . The selector  80  selects the value  1  set in advance, the piece of data output by the data memory unit  12  or data stored in the register  84  and outputs the selected one to the register  84 . The selector  80  selects one of the three inputs in accordance with a signal generated by the program control apparatus  17 . A register  87  is used for storing data representing a carry-over generated by a full adder  91 . 
     A logical product circuit  88  computes a logical product of the data stored in the register  84  and data stored in the register  85 . An exclusive logical sum circuit  89  computes an exclusive logical sum of data output by the logical product circuit  88  and data supplied by the program control apparatus  17  and supplies the exclusive logical sum to the full adder  91 . The full adder  91  also receives data stored in the register  86  and data stored in a register  87 . The full adder  91  computes the sum of these three inputs, outputting the sum and its carry-over to a selector  92 . The carry-over is also supplied to the register  87  by way of the selector  83 . 
     A selector  90  selects either the data output by the register  85  or data output by the register  86  and outputs the selected one to the selector  92 . The selector  92  selects one of three inputs thereof, that is, the data output by the selector  90 , the sum output by the full adder  91  or the carry-over also output by the full adder  91 , and outputs the selected one to the data memory unit  12 . Signals generated by the program control apparatus  17  control how the selectors  90  and  92  select one of their inputs. 
     Assume that, for example, a signal generated by the program control apparatus  17  controls the selector  80  to let the selector  80  select the value  1  to be stored in the register  84 . In this case, since the logic value  1  is stored in the register  84 , data stored in the register  85  from the data memory unit  12  passes through the logical product circuit  88  as it is, entering the full adder  91  by way of the exclusive sum circuit  89 . The full adder  91  computes the sum of the data supplied from the register  85  by way of the exclusive logical circuit  89 , data stored in the register  86  from the data memory unit  12  and data representing a carry-over generated in previous processing and stored in the register  87 . The sum and a newly generated carry-over are output to the selector  92 . The carry-over is supplied to the register  87  through to be stored therein by way of the selector  83 . 
     The program control apparatus  17  is also capable of controlling the selector  92  to select the carry-over generated by the full adder  91  to be output to the data memory unit  12 . In addition, the program control apparatus  17  is also capable of controlling the selector  90  to select either the data output by the register  85  or data output by the register  86  to be output to data memory unit  12  by way of the selector  92  which is also controlled thereby to select the data selected by the selector  90 . 
     When it is desired to supply data output by the logical product circuit  88  to the full adder  91  by logically inverting the data, the program control apparatus  17  outputs the logic value 1 to the exclusive sum circuit  89  as one of the inputs thereof. With the logic value 1 supplied to the exclusive sum circuit  89  as one of the inputs thereof, the exclusive sum circuit  89  will pass on a logic value 1 received from the logical product circuit  88  as a logic value 0 and pass on a logic value 0 received from the logical product circuit  88  as a logic value 1. 
     When it is desired to compute a logical product of newly input data and immediately previous data, the program control apparatus  17  controls the selector  80  to again select data stored in the register  84 . With the selector  80  again selecting the data stored in the register  84 , the logical product circuit  88  receives the current data and the immediately previous data and computes their logical product because the current data is stored in the register  85 . By controlling the selector  80  to select the output of the register  84  repeatedly, processing can be carried out on new input data and previous input data. 
     When processing allocated to a one horizontal scanning period as described above is finished, data processed in the one horizontal scanning period is transferred to the output SAM unit  14  by the end of the one horizontal scanning period. 
     As described above, transfers of input data stored in the input SAM unit  11  to the data memory unit  12 , processing of the data carried out by the processing circuit unit  13  and transfers of processing results to the output SAM unit  14  during the one horizontal scanning period are executed in accordance with the SIMD control program in bit units. These pieces of arithmetic/logic processing are carried out repeatedly with one horizontal scanning period of the video signal taken as a unit. 
     The data transferred to the output SAM unit  14  is further output from the output SAM unit  14  in the next horizontal scanning period. 
     As described above, three pieces of processing are carried out on each piece of input data. The three pieces of processing are the input processing to write input data into the input SAM unit  11 , the arithmetic/logic processing controlled by the program control apparatus  17  and the output processing to output results of processing from the output SAM unit  14 . The arithmetic/logic processing controlled by the program control apparatus  17  includes transfers of input data stored in the input SAM unit  11  to the data memory unit  12 , processing of the data carried out by the processing circuit unit  13  and transfers of processing results to the output SAM unit  14 . It should be noted that the three pieces of processing are executed as pipeline processing with one horizontal scanning period of the video signal taken as a unit. 
     Pay attention to data input in one horizontal scanning period. Typically, it takes as much time as about one horizontal scanning period to complete each of the three pieces of processing. Thus, in order to complete the three pieces of processing for the data, it takes as much time as about three horizontal scanning periods. Since the three pieces of processing are pipeline processing which is carried out concurrently, that is, processing wherein the 2nd piece of processing for data of the current horizontal scanning period is carried out concurrently with the 1st piece of processing for data of the following horizontal scanning period, however, it takes as much time as only about one horizontal scanning period to complete the three pieces of processing for data of one horizontal scanning period on the average. 
     In the related art data processing apparatus, pixels of one horizontal scanning period of a video signal are distributed among processor elements each for processing pixel data. However, there are a variety of formats for several hundreds to several thousands of pixels included in one horizontal scanning line of a video signal. Therefore, a data processing apparatus has to include a sufficient number of processor elements for handling a possible maximum piece count of pixel data. When such a data processing apparatus handles a video signal with few pixels, however, there is raised a problem that consumed electric power is much wasted. 
     In addition, when the number of processor elements is too small for handing pixels included in one horizontal scanning line, the horizontal scanning line is split and distributed among a plurality of data processor elements. In this case, however, a processor element allocated to data on one side of a pixel split boundary may have to exchange data with a processor element in another data processing apparatus allocated to data on the other side of the boundary. 
     If the data processing apparatus is implemented as a semiconductor chip, there is raised a problem that such exchanges of data lead to a reduced processing speed. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a data processing system that is capable of keeping up with data having a variety of sizes so as to prevent the processing speed from being lowered. 
     To achieve the above object, according to a first aspect of the present invention, there is provided a data processing system including data processing apparatuses each having a plurality of processing elements, each of the processing elements including an input unit for inputting input serial data, a processing unit for processing data input by the input unit, and an output unit for outputting results of processing carried out by the processing unit, the data processing system including: an input delaying means for causing an operation carried out by the input unit employed in a 1st one of the data processing apparatuses for inputting serial data to lag behind an operation carried out by the input unit employed in a 2nd one of the data processing apparatuses for inputting serial data; and an output delaying means for causing an operation carried out by the output unit employed in the 1st data processing apparatus for outputting serial data to lag behind an operation carried out by the output unit employed in the 2nd data processing apparatus for outputting serial data. 
     According to a second aspect of the present invention, there is provided a data processing method to be adopted in a data processing system including a plurality of data processing apparatuses each having a plurality of processing elements, each of the processing elements including an input unit for inputting input serial data, a processing unit for processing data input by the input unit; and an output unit for outputting results of processing carried out by the processing unit, the data processing method including the steps of: causing an operation carried out by the input unit employed in a 1st one of the data processing apparatuses for inputting serial data to lag behind an operation carried out by the input unit employed in a 2nd one of the data processing apparatuses for inputting serial data; and causing an operation carried out by the output unit employed in the 1st data processing apparatus for outputting serial data to lag behind an operation carried out by the output unit employed in the 2nd data processing apparatus for outputting serial data. With this configuration, for example, the input and out operations of data in the first data processing apparatus can be started after completion of the input and output operations of data of the second processing apparatus. 
     According to the data processing system and the data processing method of the present invention, an increased piece count N of data at one stage can be coped with by properly increasing the number of data processing apparatuses for processing the data. Thus, it is no longer necessary to provide a data processing apparatus with a processing performance higher than required in advance. As a result, a data processing system with a simple configuration can be implemented at a low cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a typical configuration of a related art SIMD control parallel processor; 
     FIG. 2 is a block diagram showing a typical configuration of a processing circuit unit employed in the related art SIMD control parallel processor shown in FIG. 1; 
     FIG. 3 is a block diagram showing a typical configuration of a data processing system according to the present invention; 
     FIG. 4 is a block diagram showing a typical configuration of a 2nd data processing apparatus employed in the data processing system shown in FIG. 3; 
     FIG. 5 is a block diagram showing a typical configuration of an input pointer generating circuit employed in the 2nd data processing apparatus shown in FIG. 4; 
     FIG. 6 is a block diagram showing a typical configuration of a select signal generating circuit employed in the data processing system shown in FIG. 3; 
     FIG. 7 is a block diagram showing a typical configuration of a one-word portion in a processor element in an input SAM unit employed in the 2nd data processing apparatus shown in FIG. 4; 
     FIG. 8 is a block diagram showing a typical configuration of a one-word portion in a processor element in an output SAM unit employed in the 2nd data processing apparatus shown in FIG. 4; and 
     FIG. 9 is a timing diagram illustrating the data processing system shown in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. 
     FIG. 3 is a block diagram showing a typical configuration of a data processing system according to the present invention. Components corresponding to those employed in the SIMD control processor and the processing circuit unit shown in FIGS. 1 and 2 respectively are denoted by the same reference numerals as those in FIGS. 1 and 2, and their explanation is appropriately omitted. In the typical configuration shown in FIG. 3, two data processing apparatuses  1  and  2  are provided. An inputs signal is supplied to an input SAM unit  11  employed in the 2nd data processing apparatus  1  and an input SAM unit  21  of the 1st data processing apparatus  2 . An input activating signal is supplied to input pointer generating circuits  10  and  20  employed in the data processing apparatuses  1  and  2  respectively. On the other hand, an output activating signal is supplied to output pointer generating circuits  16  and  26  employed in the data processing apparatuses  1  and  2  respectively. The output activating signal is supplied also to a select signal generating circuit  31 . Data output from an output SAM unit  14  employed in the 2nd data processing apparatus  1  and data output from an output SAM unit  24  employed in the 1st data processing apparatus  2  are supplied to a selector  30  for selecting one of them in accordance with a select signal generated by a select signal generating circuit  31 . 
     In the typical configuration shown in FIG. 3, the 2nd data processing apparatus  1  also includes a program control apparatus  17  shown in FIG. 4 in addition to the components described above such as the input SAM unit  11  to the output SAM unit  14  as is the case with the related art data processing apparatus shown in FIG.  1 . As described above, the 2nd data processing apparatus  1  is further provided with an input pointer generating apparatus  10  for generating a pointer specifying an input address in the input SAM unit  11  and the output pointer generating apparatus  16  for generating a pointer specifying an output address in the output SAM unit  14 . 
     Similarly, the 1st data processing apparatus  2  has a configuration identical with that of the 2nd data processing apparatus  1 . To put it in detail, the 1st data processing apparatus  2  also includes components such as the input pointer generating circuit  20  to a program control apparatus  27  which correspond to the input pointer generating circuit  10  to the program control apparatus  17  respectively employed in the 2nd data processing apparatus  1 . 
     The components employed in the 2nd data processing apparatus  1 , from the input SAM unit  11  to the output SAM unit  14 , constitute a plurality of processor elements  15 . Similarly, the components employed in the 1st data processing apparatus  2 , from the input SAM unit  21  to the output SAM unit  24 , constitute a plurality of processor elements  25 . 
     FIG. 4 is a block diagram showing a typical configuration of the 2nd data processing apparatus  1 . In this figure, the program control apparatus  17  which is omitted from FIG. 3 is shown. Even though not shown in any figure, the 1st data processing apparatus  2  also includes the program control apparatus  27 . 
     FIG. 5 is a block diagram showing a typical configuration of the input pointer generating circuit  10 . Even though not shown in any figure, the output pointer generating circuit  20  has the same configuration as that of the input pointer generating circuit  10 . 
     As shown in FIG. 5, a differentiation circuit  50  includes a delay circuit  54 , an inverter  55  and an AND circuit  56 . The delay circuit  54  receives a horizontal synchronization signal (a blanking signal), which is reset at an L level during a blanking period, from a circuit not shown in the figure. The blanking signal is supplied also to the AND circuit  56 . The delay circuit  54  delays the blanking signal by one block before supplying the delayed blanking signal to the inverter  55 . The inverter  55  inverts the logic of the signal supplied thereto, supplying the inverted signal to the AND circuit  56 . The AND circuit  56  computes the logical product of the signal output by the inverter  55  and the blanking signal and supplies the logical product to a reset terminal of a counter  52 . 
     Data corresponding to the delay time is loaded into a register  51  from an external apparatus. A comparator  53  compares the data stored in the register  51  with the contents of the counter  52  and outputs a result of the comparison to a stop terminal of the counter  52 . Depending upon the result of the comparison, the counting operation of the counter  52  is halted and, at the same time, the comparator  53  outputs a pulse to a line pti of the input SAM unit  11  shown in FIG. 7 as a pointer. 
     FIG. 6 is a block diagram showing a typical configuration of the select signal generating circuit  31 . In the select signal generating circuit  31  shown in the figure, a differentiation circuit  60  includes a delay circuit  64 , an inverter  65  and an AND circuit  66 . The delay circuit  64  receives the blanking signal from a circuit not shown in the figure. The delay circuit  64  delays the blanking signal by one block before supplying the delayed blanking signal to the inverter  65 . The inverter  65  inverts the logic of the signal supplied thereto, supplying the inverted signal to one of the input terminals of the AND circuit  66 . The blanking signal is supplied also to the other input terminal of the AND circuit  66  as it is. The AND circuit  66  computes the logical product of the signal output by the inverter  65  and the blanking signal and supplies the logical product to a reset terminal of a counter  62 . When a signal is supplied to the reset terminal, the counter  62  resets its contents to a zero and starts a counting operation. Data corresponding to the delay time is loaded into a register  61 . A comparator &amp; decoder  63  compares the data stored in the register  61  with the contents of the counter  62  and outputs a result of the comparison to a selector  30  as a select signal. The result of the comparison is typically the logic value 0 if the data stored in the register  61  is smaller than contents of the counter  62  or the logic value 1 if the data stored in the register  61  is greater than contents of the counter  62 . 
     FIG. 7 is a block diagram showing a typical configuration of a one-word portion in a processor element in the input SAM unit  11 . As shown in the figure, one word (32 bits) of data are supplied in parallel to lines data 0 , data 1 , data 2 , . - - , data  31  which are connected to memory cells  100 ,  101 ,  102 , . - - ,  131  respectively. The memory cells  100 ,  101 ,  102 , . - - ,  131  include transistors  100 A,  101 A,  102 A, - - - ,  131 A and transistors  100 B,  101 B,  102 B, . - - ,  131 B respectively. The base of each of the transistors  100 A,  101 A,  102 A, - - - ,  131 A is connected to a line pto for conveying the output of a shift register  90 . The input terminals of the transistors  100 A,  101 A,  102 A, - - - ,  131 A are connected to the lines data 0 , data 1 , data 2 , . - - , data  31  respectively. The output terminals of the transistors  100 A,  101 A,  102 A, - - - ,  131 A are connected to capacitors  100 C,  101 C,  102 C, - - - ,  131 C and to the input terminals of the transistors  100 B,  101 B,  102 B, . - - ,  131 B respectively. The output terminals of the transistors  100 B,  101 B,  102 B, . - - ,  131 B are connected to a read bit line. The bases of the transistors  100 B,  101 B,  102 B, . - - ,  131 B are connected to address lines address 0 , address 1 , address 2 , . - - , address 31  respectively. 
     A shift register  90  outputs data supplied thereto through the line pti to the line pto in synchronization with a clock signal supplied by a line sft. The contents of the shift register can be reset by a reset signal supplied thereto through a line rst. 
     FIG. 8 is a block diagram showing a typical configuration of the output SAM unit  14 . As shown in the figure, the output SAM unit  14  includes a shift register  190 , memory cells  200  to  231 , transistors  200 A to  231 A, transistors  200 B to  231 B and capacitors  200 C to  231 C which constitute a configuration basically identical with that of the shift register  90 , the memory cells  100  to  131 , the transistors  100 A to  131 A, the transistors  100 B to  131 B and the capacitors  100 C to  131 C employed in the input SAM unit  11  shown in FIG.  7 . 
     The difference between the input SAM unit  11  shown in FIG.  7  and the output SAM unit  14  shown in FIG. 8 is that, in the case of the former, data stored in parallel in word units in the capacitors  100 C to  131 C of the memory cells  100  to  131  from the lines data 0  to data  131  respectively is read out sequentially in bit units through the read bit line while, in the case of the latter, data stored in the capacitors  200 C to  231 C of the memory cells  200  to  231  sequentially in bit units through a write bit line is read out in parallel in word units through the lines data 0  to data 31  respectively. 
     It should be noted that processing circuit units  13  and  23  each have the same configuration as the processing circuit unit shown in FIG.  2 . 
     Next, the operation of the data processing system shown in FIG. 3 will be described. Assume that the data processing apparatuses  1  and  2  include M pieces of processor elements  15  and M pieces of processor elements  25  respectively. Also assume that an input signal conveying N pieces of data per horizontal scanning line is received in series with the pieces of data arriving sequentially where N&gt;M. In this case, the number of adjacent processor elements  15  employed in the 2nd data processing apparatus  1  that can be used jointly to process their respective pieces of pixel data is L where (M−L) has to be at least N/2. Similarly, the number of adjacent processor elements  25  employed in the 1st data processing apparatus  2  that can be used jointly to process their respective pieces of pixel data is L. 
     For the sake of convenience, in the following description, the configurations of the input pointer generating circuit  16  and the output pointer generating circuits  20  and  26  are exactly the same as the configuration of the input pointer generating circuit  10  shown in FIG.  5 . In the case described above, the contents of the registers  51  employed in the input and output pointer generating circuits  10  and  16  are each set at 0 whereas the contents of the registers  51  employed in the input and output pointer generating circuits  20  and  26  are each set at a value (M−2L). In addition, the contents of the register  61  employed in the select signal generating circuit  31  shown in FIG. 6 are set at a value (M−L). 
     For the sake of simplification, assume that M=10, N=16 and L=2. 
     In this case, when the blanking signal supplied to the input pointer generating circuit  10  shown in FIG. 5 is set at an H level, 16 pieces of pixel data P 1  to P 16  are supplied sequentially. The blanking signal is reset to an L level to indicate the start of a horizontal fly-back period during which no pixel data is supplied. In other words, the supplying of pixel data is started with timing of inversion of the blanking signal from the L level to the H level. 
     In the differentiation circuit  50 , after being delayed by the delay circuit  54  by one clock, the blanking signal is inverted by the inverter  55 . The AND circuit  56  computes the logic product of the output of the inverter  55  and the blanking signal and outputs a pulse having a width of one clock with timing of a transition of the blanking signal from the L level to the H level. The pulse resets the counter  52  which then starts to count up the number of clocks. 
     The counter  52  increments its contents by one for each clock supplied thereto. The comparator  53  compares the contents of the counter  52  with the contents of the register  51 . The comparator  53  outputs a pulse pointer for triggering an operation to read in data when the contents of the counter  52  match the contents of the register  51  to the input SAM unit  11 . Since the contents of the register  51  have been set at 0, the comparator  53  outputs a pulse as soon as the contents of the counter  52  are reset. After the pulse have been output, however, the outputting of the pulse pointer is inhibited. 
     The pulse pointer output by the comparator  53  is supplied to the shift register  90  employed in the input SAM unit  11  shown in FIG.  7  through the line pti. The contents of the shift register  90  are output sequentially to a circuit at the following stage in synchronization with a clock signal through the line pto. In the input SAM unit  11  of each processor element  15 , when the output of the shift register  90  is set at the H level, the transistors  100 A to  131 A employed in the memory cells  100  to  131  are turned on, allowing data of one word supplied from the lines data 0  to data  31  to be accumulated in the capacitors  100 C to  131 C of the memory cells  100  to  131  respectively. 
     The operation described above is carried out in the same way in each of the processor elements  15 . As a result, when the pieces of pixel data P 1  to P 16  are supplied to the data processing system, the pieces of pixel data P 1  to PM where M=10 are held in the 2nd data processing apparatus  1 . 
     On the other hand, the contents of the register  51  employed in the input pointer generating circuit  20  of the 1st data processing apparatus  2  are set at 6 (=M−2L=10−4). Much like the input pointer generating circuit  10 , the comparator  53  outputs a pulse pointer for triggering an operation to read in data when the contents of the counter  52  match the contents of the register  51  to the input SAM unit  21 . As a result, the pieces of pixel data P 7 , P 8 , P 9 , . - - , P 16  of the later part of the input signal are held in the input SAM units  21  of the respective processor elements  25  employed in the 1st data processing apparatus  2 . 
     The data held in the input SAM units  11  and  21  as described above is then transferred to the data memory units  12  and  22  respectively to be stored therein before being further transferred to the processing circuit units  13  and  23  respectively to undergo predetermined processing. 
     In the processing carried out by the processing circuit unit  13  of the 2nd data processing apparatus  1 , L adjacent pieces of pixel data where L=2 are manipulated as described above. In the case of the rightmost processor element  15 , however, there is no piece of pixel data on the right side to be processed along with the piece of pixel data for the rightmost processor element  15  as is obvious from FIG.  3 . As a result, the result of processing is not accurate. 
     Similarly, in the processing carried out by the processing circuit unit  23  of the 1st data processing apparatus  2  shown in FIG. 3, two adjacent pieces of pixel data are manipulated. In the case of the leftmost processor element  25 , however, there is no piece of pixel data on the left side to be processed along with the piece of pixel data for the leftmost processor element  25 . As a result, the result of processing is not accurate. 
     In the present embodiment, however, both the data processing apparatuses  1  and  2  redundantly process part of the input signal, that is, the four pieces of pixel data P 7  to P 10  as described above, allowing only results of processing each with an accurate value to be output. 
     To put it in detail, the comparator  53  of the output pointer generating circuit  16  employed in the 2nd data processing apparatus  1  generates a pointer so that all processing results Q 1  to Q 10  produced by the ten processor elements  15  respectively are output. Similarly, the comparator  53  of the output pointer generating circuit  26  employed in the 1st data processing apparatus  2  generates a pointer so that all processing results Q 7  to Q 16  produced by the ten processor elements  25  respectively are output. 
     As a result, the processing results Q 1 , Q 2 , Q 3 , . - - , Q 10  are output from the output SAM unit  14  of the 2nd data processing apparatus  1  and the processing results Q 7 , Q 8 , Q 9 , . - - , Q 16  are output from the output SAM unit  24  of the 1st data processing apparatus  2  as shown in FIG.  9 . The processing results are all supplied to the selector  30  employed in the data processing system shown in FIG.  3 . In particular, the processing results Q 7 , Q 8 , Q 9  and Q 10  are supplied from both the data processing apparatuses  1  and  2  to the selector  30  with the same timing. 
     The contents of the register  61  employed in the select signal generating circuit  31  shown in FIG. 6 are set at 8 (=M−L=10−2) as described above. The comparator &amp; decoder  63  compares the data stored in the register  61 , that is, the value  8 , with the contents of the counter  62  and outputs a result of the comparison to the selector  30  as a select signal. To be more specific, the result of the comparison is typically the logic value 0 if the data stored in the register  61  is greater than contents of the counter  62  or the logic value 1 if the data stored in the register  61  is smaller than contents of the counter  62 . When the select signal has the logic value 0, the selector  30  of the data processing system shown in FIG. 3 selects the processing result generated by the output SAM unit  14  employed by the 2nd data processing apparatus  1 . When the select signal has the logic value 0, on the other hand, the selector  30  selects the processing result generated by the output SAM unit  24  employed by the 1st data processing apparatus  2 . Thus, the inaccurate rightmost processing results Q 9  and Q 10  produced by the 2nd data processing apparatus  1  and the inaccurate leftmost processing results Q 7  and Q 8  produced by the 1st data processing apparatus  2  are eliminated as shown in FIG.  9 . As a result, the processing results Q 1 , Q 2 , Q 3 , . - - , Q 16  are finally output as accurate data. 
     Normally, the data processing apparatuses  1  and  2  are each built as an IC which is capable of processing data only internally, traditionally making it necessary to exchange data between the data processing apparatuses  1  and  2 . In the case of the data processing system according to the present invention, however, it is not necessary to output received pixel data. To be more specific, it is not necessary to exchange data between the data processing apparatuses  1  and  2 . As a result, it is possible to avoid the processing speed from decreasing due to the exchange of data. 
     It should be noted that the technical term ‘system’ used in this specification represents a general configuration including a plurality of apparatuses. 
     As described above, two data processing apparatuses are connected to each other in the embodiment of the present invention. It is worth noting that the number of connected data processing apparatuses can be increased as the piece count of pixel data to be processed rises. 
     While the preferred embodiment of the present invention has been described using the specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.