JP4335784B2 - Scanner image data transfer apparatus and method - Google Patents

Description

  The present invention relates to an image data transfer apparatus and method for storing image data read by a scanner once in a memory and outputting the stored image data to a PC.

  Writing of scanner image data is performed as burst data having a fixed length at a fixed interval in a period of one line of a horizontal synchronizing signal (hereinafter referred to as SHDEN-0), that is, a low level ('L') period of a pulse signal. Although it is transferred, it is not transferred at all during the pause period of the horizontal synchronizing signal, that is, the high level ('H') period of the pulse signal. In other words, even when the transfer for writing the scanner image data to the SDRAM provided in the scanner is not performed at all (SHDEN-0 = 'H'), the transfer for reading the scanner image data is always performed with the burst length fixed.

  A wasteful sequence due to repetition of an Active command, a Read command, and a PreCharge command performed with a fixed burst length reduces the transfer efficiency of reading scanner image data.

  Accordingly, an object of the present invention is to improve image data transfer efficiency when image data read by a scanner is once stored in a memory and the stored image data is output to a PC.

  The burst length is increased during a period in which the scanner image data is not transferred to the SDRAM at all (SHDEN-0 = 'H' period).

  Useless sequences due to repetition of the Active command, Read command, and PreCharge command are omitted, and the efficiency of image transfer from the SDRAM memory to the USB-I / F is increased.

  Embodiments of a scanner image data transfer apparatus and method according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of a controller for transferring a scanner read image to a PC.

  The image data read from the scanner 11 is transferred to the memory controller 13 through the image I / F of the scanner and the image I / F of the scanner I / F 12, and the memory controller 13 writes the image data into the SDRAM memory 14. The memory controller 13 reads the image data written in the SDRAM memory 14, transfers it to the USB-I / F 15, and transfers it to a personal computer (hereinafter referred to as PC) 16. When transferring the scanner read image to the PC 16, the memory controller 13 simultaneously performs the operation of writing the image data from the scanner 11 in the SDRAM memory 14 and the operation of reading the image data transferred from the SDRAM memory 14 to the PC 16.

  That is, since the scanner cannot stop the operation during image reading, the image data needs to be written to the SDRAM memory 14 at a constant speed, but the image data transferred to the PC is transferred to the USB-I / F 15 and the PC 16. It is desirable to read from the SDRAM memory 14 at the fastest transfer speed that is acceptable. However, lack of image data does not occur just because the data is transferred late. At this time, if the reading speed is faster than the writing speed, the area where the read data from the scanner 11 is not written is read, so the memory controller 13 also performs control so that the reading speed does not exceed the writing speed.

  Here, in order to write the image data of the scanner 11 in the SDRAM memory 14 without loss, the memory controller 13 executes the writing operation to the DRAM memory 14 with higher priority than the reading operation for transferring to the PC 16. Yes.

  FIG. 2 is synchronized with a horizontal synchronization signal (SHDEN-0) used between the image I / F of the scanner 11 and the image I / F of the scanner I / F 12 for transferring the image data of the scanner 11 to the memory controller 13. The image data transfer timing and the timing at which the memory controller 13 writes (writes) / reads (reads) the scanner image data in the SDRAM memory 14 are shown.

  The scanner 11 outputs image data on the image I / F in synchronization with the period 'L' of the horizontal synchronization signal (SHDEN-0). The image I / F of the scanner 11 receives the image data and transfers it to the memory controller 13 every predetermined amount (image data for 4 bursts). The memory controller 13 writes the scanner image data into the SDRAM memory 14 using burst transfer (four bursts in FIG. 2) of the SDRAM memory 14.

  The USB-I / F 15 reads the image data written in the SDRAM memory 14 and transfers it to the USB-I / F in the PC 16. The USB-I / F 15 requests the memory controller 13 to read image data in accordance with a request from the USB-I / F in the PC 16. The memory controller 13 reads the image data from the SDRAM memory 14 and transfers it to the USB-I / F 15. The USB-I / F 15 transfers the read image data to the USB-I / F of the PC 16. Even if there is no request from the USB-I / F of the PC 16, the USB-I / F 15 requests the memory controller 13 to pre-read image data from the SDRAM memory 14 if there is an empty buffer in the USB-I / F 15. There is a function to do.

  In the case of 4-burst transfer, writing / reading of data to / from the SDRAM memory 14 is performed according to the procedure of Active command → Write / Read command → data writing / reading (4 consecutive) → PreCharge command as shown in FIG. Is called. As for the writing / reading of data to / from the SDRAM memory 14, the longer the burst length, the better the transfer efficiency. Since writing of image data from the scanner 11 to the SDRAM memory 14 is preferentially performed over reading of image data from the SDRAM memory 14 to the USB-I / F 15, as shown by PMWrite in FIG. Control is performed so that writing is performed in units of one line). Since reading of image data from the SDRAM memory 14 to the USB-I / F 15 has a lower priority than writing, writing of image data of the scanner 11 to the SDRAM memory 14 is performed as indicated by PMRead in FIG. Reading is performed using a gap. When the basic clock for writing / reading of the SDRAM memory 14 is sufficiently high, the gap is wide and it can respond sufficiently to the reading request from the USB-I / F 15, but the basic clock for writing / reading of the SDRAM memory 14 cannot be increased. In such cases, the gap is narrow and the read request cannot be sufficiently responded. When the scanner image data is written to the SDRAM memory 14, the image data is transferred at a constant interval during the period when the horizontal synchronization signal (SHDEN-0) of one line is “L”. In this embodiment, (SHDEN) −0) is also transferred during the period of “H”. That is, in the period when (SHDEN-0) is 'H', the read burst length to the SDRAM memory 14 is longer than 4 bursts. As a result, useless sequences due to repetition of the Active command, the Read command, and the PreCharge command are omitted, and the image data read / transfer efficiency from the SDRAM memory 14 to the USB-I / F 15 is increased.

  That is, at the falling edge of (SHDEN-0), the mode command is used to transfer 4 bursts, and after the rising edge of (SHDEN-0), the scanner command writing (the end of one line) is completed and the mode command is used to change to the page mode. . When the page mode is changed, a burst transfer of n data corresponding to the maximum page length of the SDRAM chip specification becomes possible.

  FIG. 3 shows the relationship between the image data reading range of the scanner and the synchronization signal.

  The vertical synchronizing signal (SVDEN-0) signal is enabled by 'L' and disabled by 'H', and the enable period indicates that valid image data is output. The disable period indicates that valid image data is not output.

  The horizontal synchronizing signal (SHDEN-0) signal is enabled by 'L' and disabled by 'H', and the enable period indicates that valid image data is output. The disable period indicates that valid image data is not output.

  The image reading range indicates that both (SVDEN-0) and (SHDEN-0) signals output valid image data during the enable period.

  The (SVDEN-0) signal and the (SHDEN-0) signal are transferred to the image I / F of the scanner I / F 15 through the image I / F of the scanner 11, transferred to the memory controller 15, and written to the SDRAM memory 14. / Used for read control.

  FIG. 4 is a diagram showing the relationship between the image data reading synchronization signal of the scanner 11 that outputs a signal that repeatedly enables / disables the (SHDEN-0) signal without interruption and the mode of writing / reading image data to the SDRAM memory 14. It is.

  When the (SHDEN-0) signal has an image I / F that outputs a signal that repeats enable / disable without interruption, the memory controller 15 determines that both the (SVDEN-0) signal and the (SHDEN-0) signal are ' When the condition is L ′, the image data signal (SDAT [23: 0] −1) is written into the SDRAM memory 14. The (SDCLK [23: 0] -1) signal indicates that the rising edge of (SDCLK-1) is valid image data.

  4Burst / Page4 in FIG. 4 indicates a timing indicating whether the mode is a burst or a page mode. As indicated by this timing, the horizontal synchronization signal of the scanner 11 is displayed when the vertical synchronization signal (SVDEN-0) of the scanner 11 is enabled. (SHDEN-0) reads data transferred to the PC 16 during the enable period in the fixed-length burst transfer mode, and the horizontal synchronization signal (SHDEN-0) of the scanner 11 changes the data transferred to the PC 16 during the disable period. Read in long burst transfer mode. When the vertical synchronization signal (SVDEN-0) of the scanner 11 is disabled, data to be transferred to the PC 16 is read by variable length burst transfer.

  FIG. 5 shows an image data reading synchronization signal of the scanner in which the (SHDEN-0) signal has a signal for changing the operation in synchronization with the enable / disable of the (SVDEN-0) signal and outputting the enable / disable. 2 is a diagram showing a relationship between image data writing / reading modes to and from an SDRAM memory.

  When (SHDEN-0 signal) has a signal for changing the operation in synchronization with the enable / disable of the (SVDEN-0) signal and outputting enable / disable, the memory controller 13 (SHDEN-0) ) When the signal is the 'L' signal, the image data signal (SDAT [23: 0] -0) is written into the SDRAM memory 14. The SDCLK [23: 0] -1) signal indicates that the rising edge of (SDCLK-1) is valid image data. As indicated by the timing of 4 Burst / Page indicating 4 burst or Page mode, the data to be transferred to the PC 16 is read by fixed-length burst transfer while the horizontal synchronization signal (SHDEN-0) of the scanner 11 is enabled. When the horizontal synchronizing signal (SHDEN-0) of the scanner 11 is disabled, data transferred to the PC 16 is read by variable length burst transfer. When the vertical synchronization signal (SVDEN-0) of the scanner 11 is disabled, data to be transferred to the PC 16 is read by variable length burst transfer.

  FIG. 6 is a diagram showing the transfer timing when the variable-length burst transfer exceeds the column size boundary during the period when the (SHDEN-0) signal is 'H' at the timing of FIG.

  The variable length burst transfer in the Page mode of the SDRAM memory 14 cannot exceed the column size at the maximum. (However, the case where the data of the same column is repeatedly transferred from the beginning to the end is excluded.) This is a specification resulting from the function limitation of the SDRAM memory device. When transferring beyond the boundary of the column size, burst transfer is stopped once, and variable length burst is continued from the next column data.

  In FIG. 6, the variable length burst is started after the (SHDEN-0) signal becomes 'H' for the data of the n-1 column, the access to the n-1 column data is enabled by the Active command, To n-1 column data are burst read. Since n-1 column data has reached the boundary between n-1 column data and n column at the time of burst reading of n-1 column data, variable length burst read is stopped by Stop command, and n-1 column data is transferred to Pre-1 command by PreCharge command. Terminate access. Subsequently, the access to the n column data is enabled by the next Active command, and the data of the n column from the next of the Read command is burst read. When four pieces of n column data are read, the variable length read of the n column data is stopped by the Stop command generated by the falling edge of the (SHDEN-0) signal. Subsequently, access to the n column data is terminated by the PreCharge command. Next, the mode is changed to the 4 burst mode by the Mode command, and the mode is shifted to the fixed length burst mode.

  FIG. 7 is a diagram showing timing for realizing switching between fixed-length burst transfer and variable-length burst transfer while maintaining the Page mode of the SDRAM memory.

  Since the precharge command can stop the burst transfer and the precharge sequence can be operated in the SDRAM memory 14, the burst read transfer started when the (SHDEN-0) signal is 'L', the precharge command is performed in 4 bursts. Are sent to the SDRAM memory 14 to stop the burst and realize a fixed-length burst transfer of 4 burst transfers. Burst read transfer started when the (SHDEN-0) signal is 'H', a variable length burst is generated by sending a PreCharge command to the SDRAM memory 14 at the falling edge of the (SHDEN-0) signal to stop the burst transfer. Is realized.

  Since the transfer mode of the scanner image data to the SDRAM memory 14 is the page mode, a precharge command is sent to the SDRAM memory 14 so that four burst write operations are always performed, and a fixed burst of 4 burst write is performed. Control to be done by transfer.

  FIG. 8 is a diagram showing timing in which variable-length burst write is combined with a method for realizing switching between fixed-length burst read transfer and variable-length burst read transfer in the SDRAM page mode.

  In FIG. 7, the writing of the scanner image data to the SDRAM memory 14 is realized by the fixed burst burst transfer of 4 bursts. In FIG. 8, the writing of the scanner image data to the SDRAM memory 14 is realized by the variable length burst write transfer. It shows the timing. As shown in FIG. 7, when transfer is performed with a burst write having a fixed length of 4 bursts, a timing at which 4 burst writes are continuously performed occurs. At this time, the Active command, Write command, and PreCharge command are useless sequences. By performing 8-burst transfer with variable-length bursts, the unnecessary Active command, Write command, and PreCharge command sequence are omitted, so that the scanner image data is written to the SDRAM memory 14 even during the period (SHDEN-0 = 'L'). Transfer efficiency can be increased. When the transfer efficiency to the SDRAM memory 14 increases, the image data read transfer from the USB-I / F 15 to the SDRAM memory 14 is frequently performed, and the image data transfer time to the PC 16 can be shortened.

FIG. 1 is a block diagram of a controller for transferring a scanner read image to a PC. FIG. 2 shows image data transfer synchronized with a horizontal synchronizing signal (SHDEN-0) used between the scanner image I / F and the scanner I / F for transferring the scanner image data to the memory controller. FIG. 6 is a diagram illustrating timing and timing at which the memory controller writes / reads scanner image data to / from the SDRAM memory. FIG. 3 is a diagram showing the relationship between the image data reading range of the scanner, the synchronization signal, and the mode of writing / reading image data to / from the SDRAM memory. FIG. 4 is a diagram showing the relationship between the image data reading synchronization signal of the scanner that outputs a signal that repeatedly enables / disables the (SHDEN-0) signal without interruption and the mode of writing / reading image data to / from the SDRAM memory. . FIG. 5 shows an image data reading synchronization signal of the scanner and an SDRAM memory in which the (SHDEN-0) signal has a signal for changing the operation in synchronization with the SVDEN-0 signal enable / disable and outputting the enable / disable. FIG. 5 is a diagram showing a relationship between modes for writing / reading image data to / from the image data. FIG. 6 is a diagram showing the transfer timing when the variable-length burst transfer exceeds the column size boundary during the period when the SHDEN-0 signal is 'H' at the timing of FIG. FIG. 7 is a diagram showing timing for realizing switching between fixed-length burst transfer and variable-length burst transfer in the SDRAM page mode. FIG. 8 is a diagram showing timing in which variable-length burst write is combined with a method for realizing switching between fixed-length burst read transfer and variable-length burst read transfer in the SDRAM page mode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Scanner, 12 ... Scanner I / F, 13 ... Memory controller, 14 ... SDRAM memory, USB-I / F ... 15, Personal computer (PC) ... 16

Claims (12)

A scanner, an image memory for storing image data read from the scanner, a memory controller for controlling writing and reading of the image data to and from the image memory, and the memory controller for reading from the image memory A computer to which image data is transferred,
The image data is read and transferred by the memory controller in a fixed-length burst mode when the horizontal sync signal of the scanner is enabled, and in a variable-length burst mode when the horizontal sync signal of the scanner is disabled. A scanner image data transfer device.   2. The scanner image data transfer apparatus according to claim 1, wherein the image data is read and transferred by the memory controller in a variable length burst mode when the vertical synchronizing signal of the scanner is disabled.   The number of data that can be transferred continuously in the read transfer in the variable length burst mode is equal to or less than the column size of the image memory. When the transfer is continuously performed beyond the column size boundary, the data is divided at the column size boundary. 3. The scanner image data transfer apparatus according to claim 1, wherein the transfer is performed.   3. The scanner image data transfer apparatus according to claim 1, wherein switching between the fixed-length burst mode and the variable-length burst mode is performed at a change point of a horizontal synchronization signal of the scanner.   The fixed length burst mode starts with the first state of the horizontal synchronization signal of the scanner and stops after a predetermined number of fixed bursts are transferred, and the variable length burst mode is the second state of the horizontal synchronization signal of the scanner. 3. The scanner image data transfer device according to claim 1, wherein the scanner image data transfer apparatus starts at a state of the first and second states and stops at a time when the second state of the horizontal synchronizing signal changes to the first state.   Along with reading and transferring image data from the image memory in the fixed-length burst mode and the variable-length burst mode, the memory controller writes the image data to the image memory in a variable-length burst mode. The scanner image data transfer device according to claim 5. Storing image data read from the scanner in an image memory; reading the image data from the image memory; and transferring the image data to a computer.
The step of reading and transferring the image data is performed in a fixed-length burst mode when the horizontal synchronization signal of the scanner is in an enable period, and is performed in a variable-length burst mode when the horizontal synchronization signal of the scanner is in a disable period. Scanner image data transfer method.   8. The scanner image data transfer method according to claim 7, wherein the image data read and transfer step is performed in a variable length burst mode when the vertical synchronizing signal of the scanner is disabled.   The number of data that can be transferred continuously in the read transfer in the variable length burst mode is equal to or less than the column size of the image memory. When the transfer is continuously performed beyond the column size boundary, the data is divided at the column size boundary. 9. The scanner image data transfer method according to claim 7, wherein transfer is performed.   9. The scanner image data transfer method according to claim 7, wherein switching between the fixed-length burst mode and the variable-length burst mode is performed at a change point of a horizontal synchronization signal of the scanner.   The fixed length burst mode starts with the first state of the horizontal sync signal of the scanner and stops after the transfer of a predetermined fixed burst number, and the variable length burst mode is the second of the horizontal sync signal of the scanner. 9. The scanner image data transfer method according to claim 7, wherein the scanner image data transfer method starts at a state of the horizontal synchronization signal and stops when the horizontal state of the horizontal synchronization signal changes to the first state.   Along with reading and transferring image data from the image memory in the fixed-length burst mode and the variable-length burst mode, the memory controller writes the image data to the image memory in a variable-length burst mode. The scanner image data transfer method according to claim 11.

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