Patent Publication Number: US-11049536-B2

Title: Memory device having hardware regulation training

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of China Patent Application No. 201910660657.3, filed on Jul. 22, 2019, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a memory device and, in particular, to a memory device having hardware regulation training. 
     Description of the Related Art 
     With the widespread use of dual in-line memory modules (DIMMs) in personal computers and server systems, adjusting the data transmission of DIMMs has become an important issue. DIMM techniques have been developed to include Double-Data-Rate third generation (DDR3) DRAM and the newest Double-Data-Rate fourth generation (DDR4) DRAM. To support the operation of DDR3 and DDR4 in high-frequency environments, DIMM has adopted the topology of a Fly-by structure in order to reduce synchronous noises and improve signal integrity. 
     In the Fly-by structure, the clock signals, command signals, read/write data and addresses go through each DRAM (dynamic random access memory) particle, and the read/write data is connected to each DRAM particle. Because the clock signals, command signals, read/write data and addresses are delivered to each DRAM particle on the DIMM at different distances, there is a distinct transmission time between the read/write data reaching each DRAM particle on the DIMM. As a result, the present invention provides a memory device to make the clock period of the read/write data comply with the clock period on the DIMM when the read/write data are processed. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of this, the present invention proposes a memory device which can regulate the clock period of the read/write data in order to solve the problems mentioned above. 
     A memory device comprises a memory control unit and a write output clock device. The memory control unit is configured to provide a write input clock and a first control value. The write output clock device is configured to generate a plurality of internal clocks according to the write input clock, and select a target internal clock from among the plurality of internal clocks according to control of the memory control unit. The write output clock device delays the target internal clock based on the first control value to become a write output clock delivered to a memory unit. The memory unit generates a data signal (DQ signal) according to the write output clock, and the memory control unit receives the DQ signal and identifies whether the write output clock meets the time-sequence requirements of memory unit. If the memory control unit identifies that the write output clock fails to meet the time-sequence requirements, the memory control unit adjusts the first control value and/or the selected target internal clock for regulating the write output clock. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an operation for writing data in a memory device, in accordance with one embodiment of the present invention. 
         FIG. 2  is a block diagram of the write output clock device, in accordance with one embodiment of the present invention. 
         FIG. 3  is a block diagram of the write output clock device, in accordance with another embodiment of the present invention. 
         FIG. 4  depicts a flow chart of the operation of the write output generation device, in accordance with one embodiment of the present invention. 
         FIG. 5  is a block diagram of the operation for reading data in a memory device, in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is described with reference to the attached figures, where like reference numerals are used throughout the figures to designate similar or equivalent elements. The figures are not drawn to scale and are provided merely to illustrate the instant invention. Several aspects of the invention are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One having ordinary skill in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details, or with other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the invention. The present invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present invention. 
     The following description is an embodiment of the present invention. The purpose of the present invention is to exemplify the general principles of the invention and should not be construed as limiting the scope of the invention, which is defined by the scope of the claims. 
     There is at least one control device set in the memory device. During the period of writing data into DRAM, the control device in the memory device needs to control the data selection signal (DQS signal) between each DRAM particle to be sent at independent time, in order to comply with the time for the DQS signal reaching each DRAM particle and satisfy the time-sequence requirements, such as tDQSS, between the DQS signal and the input clock for DRAM particles. While the DRAM reads data, each DRAM particle has to adjust the time it takes to deliver the read DQS signal to the control device in the memory device, and the input clock and read DQS signal satisfy the time-sequence requirements, such as tDQSCK, for the DRAM particles. Because the clocks of the DQS signals output from different DRAM particles are not identical, the control device in the memory device needs to adjust the input selection clocks of the DQS signals output from different DRAM particles, in order to correctly deliver the data to the control device in the memory device. 
     For the operation regarding the writing/reading data of DRAM, JEDEC (Joint Electron Tube Engineering Council) provides the standards for the writing/reading regulation function of DRAM. Under JEDEC, the memory device in the present invention has the function of adjusting the write output clock of each of the DRAM particles on the data path, and the memory device is used to compensate for the write offset of the DIMM having a fly-by structure. In addition, Under JEDEC, the memory device in the present invention can adjust the clock differences of the DQS signals output from different DRAM particles in order to correctly deliver the data to the control device in the memory device. 
     The control device in the memory device can be a controller, a processor, microprocessor or central processing unit (CPU) etc., but the present invention is not so limited. 
       FIG. 1  is a block diagram of an operation for writing data in a memory device  100 , in accordance with one embodiment of the present invention. As shown in  FIG. 1 , the memory device  100  includes a memory control unit  102 , a write output clock device  104 , a write output generation device  106  and a memory unit  108  etc. In some embodiments, the memory unit  108  can be a DRAM, SDRAM (synchronous dynamic random-access memory) and so on, and the memory unit  108  has different DDR storage particles. These DDR storage particles can be connected to the memory control unit  102 , the write output clock device  104  and the write output generation device  106  via the input/output contact. 
     In some embodiments, the memory control unit  102  provides a write input clock Tin to the write output clock device  104 . The write output clock device  104  can delay the write input clock Tin to generate a write output clock Tout based on the control of the memory control unit  102 . At the same time, the write output clock device  104  initially delivers the write output clock Tout to the memory unit  108 . The DDR storage particles in the memory unit  108  generate a data signal, such as DQ signal, to the memory control unit  102  based on the write output clock Tout. According to the DQ signal of the memory unit  108 , the memory control unit  102  can identify whether the write output clock Tout complies with the time-sequence requirements. If the memory control unit  102  identifies that the write output clock Tout fails to comply with the time-sequence requirements for operating the memory unit  108 , the memory control unit  102  would control the output clock device  104  to continuously regulate the write input clock Tin for changing the write output clock Tout to memory unit  108 . 
     When the memory control unit  102  identifies that the write output clock Tout complies with the time-sequence requirements for operating the memory unit  108 , the write output clock device  104  delivers the write output clock Tout to the write output generation device  106 . At the same time, the memory control unit  102  can also provide the write input data Din to the write output generation device  106 . According to the write output clock Tout from the write output clock device  104 , the write output generation device  106  adjusts the clock period of the write input data Din for generating the write output data Dout to the memory unit  108 . In addition, the write output clock device  104  also includes a sampling unit (not pictured). The sampling unit can sample the write output clock Tout, and the sampling unit delivers the sampling result S 4  to the memory control unit  102 . According to the sampling result S 4 , the memory control unit  102  can identify if the write output clock Tout meets the time-sequence requirements of the memory unit  108 . 
     In some embodiments, the memory unit  108  can receive the write output clock Tout output by the write output clock device  104  for generating the DQ signal (or data signal) to the memory control unit  102 . In some other embodiments, the memory unit  108  can directly receive the DQS signal (or data selection control signal) from the memory control unit  102  to generate the DQ signal (or data signal) to the memory control unit  102 . According to the DQ signal, the memory control unit  102  identifies whether the write output clock Tout meets the time-sequence requirements of the memory unit  108 , but the present invention is not so limited. The procedures of the operation of the write output clock device  104  are illustrated in detail below. 
       FIG. 2  is a block diagram of the write output clock device  104 , in accordance with one embodiment of the present invention. As shown in  FIG. 2 , the write output clock device  104  includes a clock delay unit  104   a , a clock selection unit  104   b , a sampling unit  104   c , a first adjustable delay unit  104   d  and a clock phase detection circuit  104   e . The clock delay unit  104   a  is coupled to the memory control unit  102  to receive the write input clock Tin. In addition, the clock delay unit  104   a  is also coupled to the clock phase detection circuit  104   e  to receive the second control value S 2 . Based on the write input clock Tin and the second control value S 2 , the clock delay unit  104   a  generates a plurality of internal clocks to the clock selection unit  104   b . The plurality of internal clocks include a first internal clock T 1 , a second internal clock T 2 , a third internal clock T 3  and a fourth internal clock T 4 , and the first to fourth internal clocks T 1 -T 4  represent different delay clock periods. 
     In some embodiments, the first internal clock T 1  and the write input clock Tin have the same clock period. The second internal clock T 2  is delayed by a quarter of the clock period of the first internal clock T 1 . The third internal clock T 3  is delayed by half the clock period of the first internal clock T 1 . The fourth internal clock T 4  is delayed by three-quarters of the clock period of the first internal clock T 1 . However, the present invention is not so limited. 
     As mentioned above, the clock selection unit  104   b  is coupled to the memory control unit  102 , the clock delay unit  104   a  and the first adjustable delay unit  104   d . After the clock selection unit  104   b  receives the plurality of internal clocks including the first to fourth internal clocks T 1 -T 4 , based on the selection signal S 3  output by the memory control unit  102 , the clock selection unit  104   b  selects one of the plurality of internal clocks as a target internal clock T 5 . The clock selection unit  104   b  outputs the target internal clock T 5  to the first adjustable delay unit  104   d.    
     The first adjustable delay unit  104   d  is coupled to the memory control unit for receiving the first control value S 1  output by the memory control unit  102 . According to the first control value S 1 , the first adjustable delay unit  104   d  delays the clock period (or time period) of the target internal clock T 5  to generate the write output clock Tout. In view of  FIG. 1  and  FIG. 2 , the first adjustable delay unit  104   d  can deliver the write output clock Tout to the memory unit  108 , and the memory unit  108  generates the DQ signal (data signal) to the memory control unit  102  according to the write output clock Tout. If the memory control unit  102  identifies that the write output clock Tout fails to comply with the time-sequence requirements for operating the memory unit  108  based on the DQ signal, the memory control unit  102  outputs the selection signal S 3  to control the clock selection unit  104   b , and the clock selection unit  104   b  selects one of the other internal clocks which are not selected as the target internal clock T 5 . For example, if the clock selection unit  104   b  selects the first internal clock T 1  at the first time, the clock selection unit  104   b  selects one of the second to fourth internal clocks as the target internal clock T 5  at the second time. 
     At the same time, the memory control unit  102  can also adjust the first control value S 1  to the first adjustable delay unit  104   d . As a result, according to the adjusted first control value S 1 , the first adjustable delay unit  104   d  adjusts the delay clock period (or time) of the adjusted target internal clock T 5  for outputting the write output clock Tout to the memory unit  108 . When the memory control unit  102  identifies that the write output clock Tout meets the time-sequence requirements of the memory unit  108 , the memory control unit  102  stops adjusting the first control value S. The clock selection unit  104   b  stops selecting the other internal clocks, and the first adjustable delay unit  104   d  stop changing the delay clock period (or time) of the target internal clock T 5 . 
     In some other embodiments, when the memory control unit  102  identifies that the write output clock Tout fails to meet the time-sequence requirements of the memory unit  108  based on the DQ signal, the sampling unit  104   c  in the write output clock device  104  receives the first internal clock T 1  and samples the clock period of the write output clock Tout. The sampling unit  104   c  compares the first internal clock T 1  to the clock period of the write output clock Tout for outputting the sampling result S 4  to the memory control unit  102 . According to the sampling result S 4 , the memory control unit  102  can control the clock selection unit  104   b  to select one of a plurality of internal clocks as a target internal clock T 5 . 
     When the memory control unit  102  identifies that the write output clock Tout meets the time-sequence requirements of the operation of the memory unit  108 , the first adjustable delay unit  104   d  delivers the write output clock Tout to the write output generation device  106 . 
     In some other embodiments, the clock selection unit  104   b  can select the first to fourth internal clocks T 1 -T 4  in order as the target internal clock T 5 . The steps of the operation of this embodiment are illustrated in detail below. 
       FIG. 3  is a block diagram of the write output clock device  300 , in accordance with another embodiment of the present invention. Please refer to  FIGS. 1-3  for illustrating each of the following embodiments. In  FIG. 2  and  FIG. 3 , the clock delay unit  104   a  in the write output clock device  104  is composed of the second initial delay chain  302 , the second adjustable delay unit  304 , the clock reverse circuit  306  and the clock reverse circuit  308 . The clock selection unit  104   b  in the write output clock device  104  is composed of the clock selection circuits  312 ,  314  and  318  in the write output clock device  300 . The sampling unit  104   c  in the write output clock device  104  is composed of the clock selection circuit  310 , the clock selection circuit  316 , the first initial delay chain  320  and sampling circuit  322  in the write output clock device  300 . For simplifying the illustration of each of the embodiments in the present invention, the write output clock device  104  in  FIG. 1  is replaced by the write output clock device  300 . 
     As shown in  FIG. 1  and  FIG. 3 , when the write output clock device  300  receives the write input clock Tin from the memory control unit  102 , the second initial delay chain  302  generates the first internal clock T 1 . In addition, according to the second control value S 2  output by the clock phase detection circuit  104   e , the second adjustable delay unit  304  converts the write input clock Tin to the second internal clock T 2 . The first internal clock T 1  is converted as the third internal clock T 3  by the clock reverse circuit  306 , and the second internal clock T 2  is converted as the fourth internal clock T 4  by the clock reverse circuit  308 . 
     Specifically, in some embodiments, the first to fourth internal clocks T 1 -T 4  represent different delay clock periods (or time). The delay clock periods represented by the first to fourth internal clocks T 1 -T 4  have been described in detail above, and thus are not described again. In some other embodiments, the second internal clock T 2  is delayed by a quarter of the clock period of the first internal clock T 1 . The third internal clock T 3  is delayed by a quarter of the clock period of the second internal clock T 2 . The fourth internal clock T 4  is delayed by a quarter of the clock period of the third internal clock T 3 . However, the present invention is not so limited. 
     In some embodiments, as shown in  FIG. 1 , when the memory control unit  102  outputs the DQS signal to the memory unit  108 , the DRAM particles in the memory unit  108  will generate a DQ signal (or data signal) to the memory control unit  102  according to its own write regulation function. The memory control unit  102  receives the DQ signal (or data signal). According to the DQ signal, the memory control unit  102  identifies whether the write output clock Tout meets the time-sequence requirements of the operation of the memory unit  108 . Specifically, in some other embodiments, by receiving the write output clock Tout, the memory unit  108  can also generate the DQ signal to the memory control unit  102 , but the present invention is not so limited. 
     Because the different firmware units are configured in the memory control unit  102 , the methods for determining the time-sequence requirements by the memory control unit  102  according to the DQ signal (or data signal) are not completely identical. When the memory control unit  102  receives the potential of the DQ signal which is “0”, it represents that the write output clock Tout (or the DQS signal) transmitted to DRAM particles is ahead of time-sequence requirements. Therefore, the memory control unit  102  delays the write output clock Tout. When the memory control unit  102  receives the potential of the DQ signal which is “1”, it represents that the write output clock Tout (or DQS signal) transmitted to DRAM particles meets the time-sequence requirements. However, the present invention is not so limited. 
     In  FIG. 1  and  FIG. 3 , when the memory control unit  102  identifies that the write output clock Tout fails to meet the time-sequence requirements, the memory control unit  102  begins to the steps of delaying the write output clock Tout (or the steps of hardware regulation). At the initial step, according to the selection signal S 3   a  output by the memory control unit  102 , the clock selection circuit  312  in the write output clock device  300  can select and adjust the first internal clock T 1  to the clock selection circuit  318 . Then, the clock selection circuit  318  receives the adjusted first internal clock T 1  and the selection signal S 3   c  which is from the memory control unit  102  to generate the target internal clock T 5 . At the same time, the initial setting of the first control value provided by the memory control unit  102  is zero, but the present invention is not so limited. The first adjustable delay unit  104   d  receives the first control value S 1  (equal to zero) and the target internal clock T 5  to generate the write output clock Tout. At this time, the total delay period of the write output clock Tout is the sum of the delays of the second initial delay chain  302 , the clock selection circuit  312  and  318 , and the first adjustable delay unit  104   d.    
     In the initial step, if the DQ signal generated by the memory unit  108  according to the write output clock Tout is still determined by the memory control unit  102  to not meet the time-sequence requirements, the memory control unit  102  would increase the first control value S 1  to the first adjustable delay unit  104   d  to increase the delay clock period of the write output clock Tout. When the memory control unit  102  increases the first control value S 1  that is equal to the second control value S 2 , the memory control unit  102  stops the initial step. Specifically, in the initial step, before the first control value S 1  is equal to the second control value S 2 , the initial step of delaying the write output clock Tout is stopped as long as the memory control unit  102  determines that the write output clock Tout meets the time-sequence requirements. When the first control value S 1  is equal to the second control value S 2 , if the memory control unit  102  determines that the write output clock Tout fails to meet the time-sequence requirements, the memory control unit  102  stops the initial step of the hardware regulation and performs the second step of the hardware regulation. 
     In the second step of the hardware regulation, the clock selection circuit  312  in the write output clock device  300  selects and adjusts the second internal clock T 2  to the clock selection circuit  318  according to the selection signal S 3   a  output by the memory control unit  102 . Then, the clock selection circuit  318  receives the selection signal S 3   c  from the memory control unit  102  and the adjusted second internal clock T 2  to generate the target internal clock T 5 . At the same time, the first control value S provided by the memory control unit  102  is reset to zero, but the invention is not limited thereto. The first adjustable delay unit  104   d  receives the first control value S 1  (equal to zero) and the target internal clock T 5  to generate a write output clock Tout. At this time, the total delay period of the write output clock Tout is the sum of the delays of the second initial delay chain  302 , the clock selection circuits  312  and  318 , and the first adjustable delay unit  104   d . That is, the total delay of the write output clock Tout in the second step is as the same as the total delay of the write output clock Tout in the initial step. 
     In the second step, if the DQ signal generated by the memory unit  108  according to the write output clock Tout is still determined by the memory control unit  102  to not meet the time-sequence requirements, the memory control unit  102  adds the first control value S 1  to the first adjustable delay unit  104   d  for increasing the delay clock period of the write output clock Tout. In the second step, unlike the initial step, the write output clock device  300  samples the write output clock Tout through the sampling circuit  322 , and the sampling circuit  322  compares the sampled write output clock Tout with a reference clock Tref to output the sampling result S 4  to the memory control unit  102 . The sampling unit  104   c  in  FIG. 2  can be composed of the clock selection circuits  310  and  316 , the first initial delay chain  320  and the sampling circuit  322  in  FIG. 3 . It should be noted that the clock selection circuits  310  and  316  and the first initial delay chain  320  delay the first internal clock T 1  to generate the reference clock Tref. 
     In the second step, the memory control unit  102  determines whether the write output clock Tout meets the time-sequence requirements according to the sampling result S 4 . Since different firmware is configured in the memory control unit  102 , the ways in which the memory control unit  102  determines the time-sequence requirements according to the sampling result S 4  are not completely identical. For example, when the potential of the sampling result S 4  received by the memory control unit  102  is “1”, it represents that the write output clock Tout transferred to the DRAM particles still fails to meet the time-sequence requirements. Therefore, when the potential of the sampling result S 4  received by the memory control unit  102  is “0”, the memory control unit  102  stops the second step of performing the hardware regulation. However, the invention is not limited thereto. 
     When the potential of the sampling result S 4  received by the memory control unit  102  is “0”, the sum of the delays of the write output clock Tout is the sum of the delays of the first initial delay chain  320 , the second initial delay chain  302 , the clock selection circuits  310  and  316 , and the delay of the ½ clock period. At the same time, the sum of the delays of the write output clock Tout is also as the same as the sum of the delays of the following components: the second adjustable delay unit  304 , the clock selection circuits  312  and  318 , and the first adjustable delay unit  104   d.    
     When the potential of the sampling result S 4  received by the memory control unit  102  is “0”, if the memory control unit  102  determines that the write output clock Tout fails to meet the time-sequence requirements according to the DQ signal, the memory control unit  102  continues to perform the third step of the hardware regulation. 
     In the third step, the memory control unit  102  outputs the selection signals S 3   b , S 3   c  to control the write output clock device  300 . At this time, the write output clock device  300  selects the third internal clock T 3  output from the clock reverse circuit  306 , and the write output clock device  300  generates the target internal clock T 5  through the clock selection circuits  314  and  318  to output the write output clock Tout. In the initial third step, the memory control unit  102  resets the first control value S 1  to zero. If the memory control unit  102  still determines that the DQ signal generated by the memory unit  108  according to the write output clock Tout fails to meet the time-sequence requirements, the memory control unit  102  increases the first control value S 1  to the first adjustable delay unit  104   d  for increasing the delay clock period of the write output clock Tout. When the first control value S 1  increased by the memory control unit  102  is equal to the second control value S 2 , the memory control unit  102  stops the third step. The delay process in the third step is similar to the initial step of the hardware regulation. The significant difference is that the initial step generates the target internal clock T 5  according to the first internal clock T 1 , and the third step generates the target internal clock T 5  according to the third internal clock T 3 , so it will not be described again. 
     In the third step, when the first control value is identical to the second control value, if the memory control unit  102  determines that the write output clock Tout fails to meet the time-sequence requirements according to the DQ signal, the memory control unit  102  stops the third step of the hardware regulation and performs the fourth step of the hardware regulation. 
     In the fourth step, the memory control unit  102  outputs the selection signals S 3   b  and S 3   c  to control the write output clock device  300 . At this time, the write output clock device  300  selects the fourth internal clock T 4  output by the clock reverse circuit  308  and generates the target internal clock T 5  through the clock selecting circuits  314  and  318  to output the write output clock Tout. The delay process in the fourth step is similar to the initial step of the hardware regulation. The difference is that the initial step generates the target internal clock T 5  according to the first internal clock T 1 , and the fourth step generates the target internal clock T 5  according to the fourth internal clock T 4 , so it will not be described again. 
     Through the initial step to the fourth step of the hardware regulation mentioned above, it is ensured that the write output clock Tout output by the write output clock device  300  meets the time-sequence requirements of the memory unit  108 . In particular, the initial step to the fourth step of the hardware regulation can also ensure that the delay of the write output clock Tout is continuous and linearly increased. In addition, by the four steps of the hardware regulation above, the adjustment of the first control value S 1  and the switching of the first to fourth internal clocks T 1 -T 4  can ensure that the delay of the write output clock Tout with respect to the write input clock Tin is continuous and linearly increased. 
     After the write output clock Tout is completed according to the hardware regulation of the memory device, the memory control unit  102  generates the write output data Dout to the memory unit  108  via the write output generation device  106 . The operation process for generating the write output data Dout will be described in detail below. 
       FIG. 4  depicts a flow chart of the operation of the write output generation device  106 , in accordance with one embodiment of the present invention. As shown in  FIG. 4 , the write output generation device  106  includes first to fourth data sampling circuits  106   a - 106   d  and a data selection circuit  106   e . The write output generation device  106  is coupled to the memory control unit  102  to receive the write input data Din, and the write output generation device  106  is further coupled to the write output clock device  104  to receive the first to fourth internal clocks T 1 -T 4  and the write output clock Tout. When the memory control unit  102  completes the hardware regulation&#39;s steps mentioned above to output an appropriate write output clock Tout, the write output clock device  104  delivers the first to fourth internal clocks T 1 -T 4  to the write output generation device  106 . Simultaneously, the memory control unit  102  also outputs the write input data Din to the write output generation device  106 . 
     The first data sampling circuit  106   a  in the write output generation device  106  receives the write input data Din and the third internal clock T 3 . The first data sampling circuit  106   a  adjusts the clock period of the write input data Din according to the third internal clock T 3 , and the first data sampling circuit  106   a  outputs the first internal data D 1  to the data selection circuit  106   e.    
     The second data sampling circuit  106   b  in the write output generation device  106  receives the write input data Din and the fourth internal clock T 4 . The second data sampling circuit  106   b  adjusts the clock period of the write input data Din in accordance with the fourth internal clock T 4 . The second data sampling circuit  106   b  outputs the second internal data D 2  to the data selection circuit  106   e.    
     The third data sampling circuit  106   c  in the write output generation device  106  receives the first internal data D 1  and the first internal clock T 1  output from the first data sampling circuit  106   a . The third data sampling circuit  106   c  adjusts the clock period of the first internal data D 1  in accordance with the first internal clock T 1 . The third data sampling circuit  106   c  outputs the third internal data D 3  to the data selection circuit  106   e.    
     The fourth data sampling circuit  106   d  in the write output generation device  106  receives the first internal data D 1  and the second internal clock T 2  output from the first data sampling circuit  106   a . The fourth data sampling circuit  106   d  adjusts the clock period of the first internal data D 1  in accordance with the second internal clock T 2 , and the fourth data sampling circuit  106   d  outputs the fourth internal data D 4  to the data selection circuit  106   e.    
     As described above, all of the first to fourth internal clocks T 1 -T 4  are generated by the write output clock device  104  according to the write input clock Tin. The write output generation device  106  samples the first internal data D 1  based on the first internal clock T 1  for generating the third internal data D 3 . The write output generation device  106  samples the first internal data D 1  based on the second internal clock T 2  for generating the fourth internal data D 4 . The write output generation device  106  samples the write input data Din based on the third internal clock T 3  for generating the first internal data D 1 . The write output generation device  106  samples the write input data Din based on the fourth internal clock T 4  for generating the second internal data D 2 . As a result, the first to fourth internal data D 1 -D 4  respectively correspond to the third internal clock T 3 , the fourth internal clock T 4 , the first internal clock T 1  and the second internal clock T 2  in order. 
     In some embodiments, the data selection circuit  106   e  in the write output generation device  106  selects the first to fourth internal data D 1 -D 4  in accordance with the write output clock Tout output by the write output clock device  104  to output the write output data Dout. For example, if the write output clock Tout is the first internal clock T 1 , the data selection circuit  106   e  selects the third internal data D 3  corresponding to the first internal clock T 1  as the write output data Dout, according to the write output clock Tout. If the write output clock Tout is the third internal clock T 3 , the data selection circuit  106   e  selects the first internal data D 1  corresponding to the third internal clock T 3  as the write output data Dout, in accordance with the write output clock Tout, and so on. In this way, it can be ensured that the write output data Dout output by the data selection circuit  106   e  meets the time-sequence requirements. Specifically, the embodiments described above are merely illustrative, but the invention is not limited thereto. 
     In some other embodiments, the data selection circuit  106   e  may also select the first to fourth internal data D 1 -D 4  as the write output data Dout according to the DQS signal (or data selection control) output by the memory control unit  102 . Because the memory control unit  102  can identify the internal clock (one of the first to fourth internal clocks T 1 -T 4 ) selected by the write output clock device  104  as the write output clock Tout, the memory control unit  102  can generate a control signal (e.g., a DQS signal) to the data selection circuit  106   e  based on the selected internal clock. Therefore, by outputting the DQS signal, the memory control unit  102  controls the data selection circuit  106   e  to select the first to fourth internal data D 1  to D 4  as the write output data Dout. 
     In addition to the clock cycle adjustment of the operation of writing data from the memory control unit  102  to the memory unit  108 , the present invention can also perform operations for reading data from the memory unit  108  to the memory control unit  102 . Clock cycle adjustment. 
       FIG. 5  is a block diagram of an operation for reading data in a memory device  200 , in accordance with one embodiment of the present invention. As shown in  FIG. 5 , the memory device  200  includes a memory control unit  102 , a read input selection circuit  103 , a read input sampling circuit  105 , a read input sampling-selection generation circuit  107  and a memory unit  108 . The memory control unit  102  controls the read input sampling-selection generation circuit  107  to generate a read sampling clock Tr to the memory unit  108 . The read input sampling-selection generation circuit  107  has the same circuit architecture as the write output clock device  104  in  FIG. 1 . In addition, the memory control unit  102  can also control the read input selection circuit  103  and the read input sampling circuit  105  by read input sampling-selection generation circuit  107 . 
     In some embodiments, when the memory unit  108  receives the read sampling clock Tr, the memory unit  108  outputs the DQS signal. The memory control unit  102  samples the DQS signal by the read input selection circuit  103  and the read input sampling circuit  105 , and the memory control unit  102  determines whether the sampling result meets the time-sequence requirements of the read input data of the memory control unit  102 . 
     Since different firmware is configured in the memory control unit  102 , the ways in which the memory control unit  102  determines the time-sequence requirements according to the DQS signals are not completely identical. For example, when the potential of the DQS signal sampled by the memory control unit  102  is “0”, it represents that the DQS signal fails to meet the time-sequence requirements of the read input data of the memory control unit  102 , and the memory control unit  102  adjusts the read sampling clock Tr. When the potential of the DQS signal sampled by the memory control unit  102  is “1”, it indicates that the DQS signal meets the time-sequence requirements of the read input data of the memory control unit  102 . However, the invention is not so limited. 
     The operation mentioned above ensures that the clock period of the read selection signal S 5  output by the read input sampling-selection generation circuit  107  is ¼ clock period earlier than the read sampling clock Tr. As a result, the read input selection circuit  103  advances by ¼ of the clock period of the DQS signal received by the memory control unit  102 . This ensures that the input signal (including the DQS signal and the read input data Dr) can be completely delivered to the memory control unit  102 . 
     In conclusion, the operation methods of the hardware regulation for a clock, which are proposed by the present invention, can process the clock regulation to the write output clock Tout and read sampling clock Tr. This can ensure that a clock that is adjusted by the hardware regulation can satisfy the monotonic continuity requirements of memory units (include DRAM), which have different operation frequencies. Thus, the write regulation mechanism and the read regulation mechanism of the present invention can make sure that the memory unit satisfies time-sequence requirements such as tDQSS, between the input clock and DQS signal for DRAM particles. Each of the DRAM particles can also output data in accordance with the time-sequence requirements (e.g., tDQSCK) while the memory control unit is reading the data. 
     While the invention has been described above in terms of a preferred embodiment, it is not intended to limit the scope of the invention, and it should be understood by those of ordinary skill in the art without departing from the spirit and scope of the invention. Instead, the scope of the invention should be determined by the scope of the appended claims. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”