JP2013130952A - Data transferring apparatus and data transferring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in the conventional techniques in which a packet is not compressed in a transfer having a large difference from the last transfer but having a small difference from the second last or third last transfer because only the difference from the last transfer is considered, so that transfer efficiency is not improved.SOLUTION: A data transferring apparatus that transfers data using a packet retains transfer attribute information on a plurality of past transfers; and executes a transfer, when its transfer attribute information matches that of a past transfer, without the transfer attribute information but with the addition of an identifier indicating which past transfer it matches, so as to reduce the size of a packet and improve transfer efficiency.

Description

  The present invention relates to a data transfer apparatus and a data transfer method for performing data transfer using a packet.

Techniques for transferring data using packets are applied in various fields. TCP / IP (Transmission Control Protocol / Internet Protocol) is a technology that performs data transfer on the Internet on a packet basis. PCI-Express (Peripheral Component Interconnect-Express) is a technique for performing data transfer between integrated circuits on a packet basis. In addition, NoC (Network On Chip) is a technique for performing data transfer in an integrated circuit on a packet basis. An advantage of performing data transfer on a packet basis is that various information necessary for transfer of addresses, data, and the like can be transferred with a small number of signal lines as a set. For example, in PCI-Express, data transfer can be performed using only two pairs of differential lines. Another advantage of transferring data on a packet basis is that it is easy to increase the transfer rate.
However, the packet-based transfer method has a problem in that the number of cycles required for transfer is larger than that of the non-packet-based transfer method because various information is developed and transmitted on the time axis. Therefore, a technique has been proposed in which the packet structure is devised and only the minimum necessary information is transferred, thereby reducing the number of cycles required for transfer and increasing transfer efficiency. As an example, V.V. defined in RFC1144 disclosed in Non-Patent Document 1 is described. There is a header compression method of Jacobson. V. In the header compression method of Jacobson, the packet of the previous transfer is compared with the packet to be transferred, and only the information with the difference is transferred, so that the packet is compressed and the transfer efficiency is improved. Yes.

RFC 1144 Compressing TCP / IP Headers February 1990

  In the conventional technique such as Non-Patent Document 1, since only the difference from the immediately preceding transfer is considered, the compression efficiency is not good, and it is difficult to improve the transfer efficiency.

In order to solve the above problems, a data transfer apparatus according to the present invention receives a transfer request including a holding unit that holds a plurality of packet attribute information in association with a first identifier, and attribute information indicating a type of data transfer. If the attribute information received by the receiving means matches the attribute information held by the holding means, the attribute information received by the receiving means matches with which attribute information held by the holding means Transmitting means for transmitting the first identifier indicating whether or not to be included in the packet instead of the attribute information received by the receiving means.
The data transfer apparatus according to the present invention includes a holding unit that holds a plurality of packet attribute information in association with the first identifier, a receiving unit that receives a transfer request including the first identifier, and a holding unit that holds the packet. Transmission means for transmitting the attribute information corresponding to the first identifier received by the receiving means included in the packet instead of the identifier received by the receiving means.

  Even if the difference from the previous transfer is large, the packet can be compressed and the transfer efficiency can be improved when the difference from the previous transfer or the previous transfer is small.

The system configuration is shown. The structure of the bus bridge in one Embodiment of this invention is shown. Indicates the format of the packet. 3 shows a packet identifier in one embodiment of the present invention. Indicates the serial bus format. The timing chart in 1st embodiment of a prior art example and this invention is shown. It is the schematic which shows the structure of the communication system between chips. It is a figure which shows an AXI bus protocol. The table which a log | history holding part hold | maintains is shown.

<Embodiment 1>
Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.

  FIG. 7 shows a configuration example of an inter-chip communication system including the data transfer apparatus according to the first embodiment of the present invention. The CPU 901, ROM 902, and RAM 903 are connected to the first bus 909, and the PCI 906, USB 907, and IDE 908 are connected to the second bus 910. The first bus 909 and the second bus 910 are connected via a bridge 904 and a bridge 905. This configuration is a typical configuration of a two-chip set in a general-purpose computer, and includes a chip including a bridge 904 and a chip including a bridge 905.

  The CPU 901 expands the program in the ROM 902 in the RAM 903, reads the program from the RAM, and executes it. The PCI 906, USB 907, and IDE 908 connected to the second bus are control units that control connection with various peripheral devices (not shown).

  The bridge 904 transfers a data transfer request (read request, write request, etc.) transmitted according to the protocol of the first bus 909 by the CPU or DMAC (not shown) to the bridge 905 by inter-chip connection. Note that the write request includes data in the RAM 903, a register value (not shown), and the like. The bridge 905 transfers the data acquired from the bridge 904 to various peripheral circuits according to the protocol of the second bus 910. The data transfer request includes attribute information indicating the type of data transmission method (burst length, exclusive attribute, security information, presence / absence of cache use) used for transferring the data to be transferred. For example, data to be read by read access to PCI 906, USB 907, and IDE 908 from CPU or DMAC (not shown) and data to be written by write access are transferred in the data transfer type indicated by this attribute information.

  Here, the response to the request (read data, request completion notification, etc.) is transmitted from the request transmission destination to the request transmission source. In that case, since the protocol conversion is performed in reverse to the case of the request through the bridge 905 and the bridge 904, the description is omitted.

  The configuration of the inter-chip communication system including the data transfer apparatus according to the first embodiment is not limited to the configuration of FIG.

  FIG. 1 shows a configuration of a system in which ASIC_A 100 and ASIC_B 200 are connected by a serial bus 300. (ASIC is an abbreviation for Application Specific Integrated Circuit.) On serial bus 300, data transfer is performed using packets. The ASIC_A 100 includes a first bus master A 101, a first bus master B 102, a first bridge 103, and a DRAM controller A 104, and each module is connected by a first bus 105. The first bus 105 is a parallel bus in which addresses, data, and the like are connected by dedicated lines.

  The first bus master A 101 and the first bus master B 102 transfer data between the first bridge 103 and the DRAM controller A 104 via the first bus 105. The DRAM controller A104 performs data transfer with the DRAM_A106 via the DRAM I / F A107. The first bridge 103 converts the transfer from the first bus 105 to the transfer of the serial bus 300 and transfers the transfer to the second bridge 203 in the connection destination ASIC_B 200. On the other hand, the ASIC_B 200 includes a second bus master A 201, a second bus master B 202, a second bridge 203, and a DRAM controller B 204, and each module is connected by a second bus 205. The second bus 205 is a parallel bus in which addresses, data, and the like are connected by dedicated lines.

  The second bridge 203 converts the transfer from the serial bus 300 to the transfer of the second bus, and transfers it to the DRAM controller B 204 via the second bus. The second bus master A 201 and the second bus master B 202 perform data transfer with the DRAM controller B 204 via the second bus 205. The DRAM controller B204 performs data transfer with the DRAM_B206 via the DRAM I / F B207. The first bus masters A and B and the second bus masters A and B output requests as bus masters such as the CPU 901 shown in FIG. 7 and PCI 906, USB 907, IDE 908 for controlling connection with various peripheral devices, and DMAC (not shown). Any configuration may be used.

  FIG. 2 is a configuration diagram of the first bridge 103 and the second bridge 203 for realizing the transfer method of the present embodiment. Each process of the bridge will be described below.

[Request transmission processing]
First, transmission processing of a data transfer request (write request, read request, etc., simply referred to as a request hereinafter) by the first bridge 103 will be described. The first bus request receiving unit 1030 receives requests from the first bus master A 101 and the first bus master B 102 via the first bus 105. The request includes a transfer destination address (Address), a flag indicating whether Write transfer or Read transfer, write data (Wdata), strobe (Wstrb), and transfer attribute information (ReqAtrb0 / 1).

  The transfer attribute information (ReqAtrb0 / 1) includes information indicating the transfer length, transfer priority, and the like. The request transmission history holding unit 1036 holds a plurality of transfer attribute information (ReqAtrb0 / 1) transferred in the past. An example of information held in the request transmission history holding unit 2036 is shown in FIG. The request packet conversion unit 1031 converts the received request into one or more packets.

  Here, the packet converted by the request packet conversion unit 1031 is shown in FIGS. A packet is composed of a header and data. Both the header and the data are composed of a plurality of characters having a predetermined length (32 bits). The header includes an identifier (Type) indicating the type of packet, transfer attribute information (ReqAtrb0 / 1), and a transfer destination address (Address). The data is composed of write data (Wdata) and strobe (Wstrb), and is generated at the time of Write transfer.

  Hereinafter, packet conversion processing in the request packet conversion unit 1031 will be described in detail. The request packet conversion unit 1031 refers to the past transfer attribute information (ReqAtrb0 / 1) held in the request transmission history holding unit 1036 when converting a request from the first bus into a packet, and matches Make a comparison. Then, the request packet conversion unit 1031 converts the packet into a packet according to the comparison result.

  When the comparison results do not match, the transfer attribute information (ReqAtrb0 / 1) is added to the packet as shown in FIG. At this time, the identifier added to the packet is an identifier indicating that the transfer attribute information (ReqAtrb0 / 1) is added, and is “00000” for Read transfer and “01000” for Write transfer. Further, the transfer attribute information (ReqAtrb0 / 1) is held in the request transmission history holding unit 1036. However, if the request transmission history holding unit 1036 holds a predetermined number of transfer attribute information (ReqAtrb0 / 1) (for example, holds the maximum number that can be held), the oldest transfer held. Attribute information (ReqAtrb0 / 1) is deleted. Instead, transfer attribute information (ReqAtrb0 / 1) to be transferred is held.

  On the other hand, when the comparison results match, the transfer attribute information (ReqAtrb0 / 1) is not added to the packet as shown in FIG. At this time, the identifier added to the packet is an identifier indicating which transfer attribute information (ReqAtrb0 / 1) held in the request transmission history holding unit 1036 matches the transfer attribute information (ReqAtrb0 / 1).

  FIG. 4 shows details of the identifier added in the packet conversion process. In the present embodiment, the request transmission history holding unit 1036 stores transfer attribute information of up to four packets transferred in the past as shown in FIG. The most significant bit of the identifier is an identifier (second identifier) indicating whether or not it matches the past transfer information. If it is 0, it indicates that it does not match, and if it is 1, it indicates that it matches. The second bit from the top of the identification is an identification indicating whether it is Read transfer or Write transfer. If it is 0, it indicates Read transfer, and if it is 1, it indicates Write transfer. The third bit from the top of the identification is the identification indicating whether it is a request or a response. If it is 0, the request indicates a response. The lower 2 bits (first identifier) of the identifier indicate which combination is matched when matched with past transfer information. For example, if the lower 2 bits are “00”, it matches the combination 1, and if the lower 2 bits are “01”, it matches the combination 2. For example, if the combination 3 of transfer attribute information in the past and the transfer attribute information match at the time of Read transfer, the identifier of the packet to be transferred this time is “10010”. Note that the transfer attribute information shown in FIG. 9 corresponds to AXI (Advanced extensible Interface), details of which will be described later.

  The packet generated by the request packet conversion unit 1031 according to the present embodiment is not only the previous transfer but also the packet at the time when the previous transfer and the transfer attribute information (ReqAtrb0 / 1) match. The packet is one character fewer than The request packet transmission unit 1032 performs parallel-serial conversion on the request converted into the packet and transmits the request to the serial bus 300.

  An example of parallel-serial conversion is shown in FIG. In FIG. 5, “N” indicates a non-transfer period (NOP), and “S” indicates a start bit. The number indicates the bit position in the character. Parallel-serial conversion is performed for each character in units of 32 bits. First, a 2-bit start bit indicating the head of the character is added to the 32-bit unit character. A 2-bit start bit is transmitted. Thereafter, transmission is performed 1 bit at a time in order from the most significant bit of the 32-bit character. The parallel-serial converted character is transmitted to the receiving side ASIC_B 200 through the serial bus 300 together with the clock.

[Request reception processing]
Next, a request reception process by the second bridge 203 will be described. The request packet receiving unit 2030 receives the character transmitted from the ASIC_A 100 via the serial bus 300 and performs serial-parallel conversion. Serial-parallel conversion is performed for each character in units of 32 bits. First, a 2-bit start bit is recognized. If the 2-bit start bit is recognized, the subsequent 32-bit serial data is received and converted into parallel data to generate a 32-bit character.

  The request reception history holding unit 2036 holds a plurality of transfer attribute information (ReqAtrb) transferred in the past. An example of information held in the request reception history holding unit 2036 is shown in FIG. The request packet reverse conversion unit 2031 performs processing for converting a packet including an identifier (Type) indicating the type of transfer into a request format to the second bus. Since the detailed description of the identifier is the same as the description of the request transmission process, it is omitted here. If the identifier indicating the packet type indicates that the transfer attribute information (ReqAtrb0 / 1) is added, the transfer attribute information (ReqAtrb0 / 1) is extracted from the received packet, and a request to the second bus is made. Convert to format. Further, the extracted transfer attribute information (ReqAtrb0 / 1) is held in the request reception history holding unit 2036. However, if the number of transfer attribute information (ReqAtrb0 / 1) held in the request reception history holding unit 2036 is the maximum number that can be held, the oldest transfer attribute information (ReqAtrb) held is deleted. . Instead, the received transfer attribute information (ReqAtrb0 / 1) is held.

  On the other hand, if the identifier indicating the packet type indicates that the transfer attribute information (ReqAtrb0 / 1) is not added, the request packet reverse conversion unit 2031 transfers the transfer attribute held in the request reception history holding unit 2036. Information (ReqAtrb0 / 1) is referred to. For example, if the identifier is “10010”, the transfer attribute information of the combination 3 is referred to. Then, using the transfer attribute information (ReqAtrb0 / 1) corresponding to the identifier, it is converted into a request format to the second bus. The second bus request transmission unit 2032 transmits the request converted into the request format for the second bus to the DRAM controller B 204 via the second bus 205.

[Response transmission processing]
Next, a response transmission process by the second bridge 203 will be described. The second bus response receiving unit 2033 receives a response from the DRAM controller B 204 via the second bus 205. The response includes status information (RespSt) indicating whether or not an error, read data (Rdata), and transfer attribute information (RespAtrb0 / 1) indicating the transfer length and transfer priority. The response transmission history holding unit 2037 holds transfer attribute information (RespAtrb0 / 1) of at least two past transfers. An example of information held in the response transmission history holding unit 2037 is shown in FIG. The response packet conversion unit 2034 converts the received response into a packet. Examples of packets to be converted are shown in FIGS. 3 (c) and 3 (d). A packet is composed of a header and data. Both the header and data are composed of a plurality of 32-bit unit characters. The header includes an identifier (Type) indicating the type of transfer, a status (RespSt), and transfer attribute information (RespAtrb0 / 1). FIG. 4 shows examples of identifiers. Since the detailed description of the identifier is the same as the description of the request transmission process, it is omitted here. The data is constituted by read data (Rdata) and is generated only at the time of Read transfer. Hereinafter, packet conversion processing in the response packet conversion unit 2034 will be described in detail.

  The response packet conversion unit 2034 refers to the past transfer attribute information (RespAtrb0 / 1) held in the response transmission history holding unit 2037 when converting the response from the second bus into a packet, and matches Make a comparison. Depending on the comparison result, conversion into a different packet is performed.

  When the comparison results do not match, the transfer attribute information (RespAtrb0 / 1) is added to the packet as shown in FIG. The transfer identifier at this time is an identifier indicating that transfer attribute information (RespAtrb0 / 1) is added, and is “00100” for Read transfer and “01100” for Write transfer. Also, the transfer attribute information (RespAtrb) is held in the response transmission history holding unit 2037. However, if the number of transfer attribute information (RespAtrb0 / 1) held in the response transmission history holding unit 2037 is the maximum number that can be held, the oldest transfer attribute information (RespAtrb0 / 1) held is changed. delete. Instead, transfer attribute information (RespAtrb0 / 1) to be transferred is held.

  On the other hand, when the comparison results match, the response packet conversion unit 2034 does not add the transfer attribute information (RespAtrb0 / 1) to the packet as shown in FIG. The transfer identifier at this time is an identifier indicating which transfer attribute information (RespAtrb0 / 1) held in the response transmission history holding unit 2037 matches the transfer attribute information (RespAtrb0 / 1).

  FIG. 4 shows examples of identifiers. Since the detailed description of the identifier is the same as the description of the request transmission process, it is omitted here. The packet generated by the response packet conversion unit 2034 of the present embodiment is not only the previous transfer, but if the previous several transfers and the transfer attribute information (RespAtrb0 / 1) match, the packet when it does not match The packet is one character fewer than

  The response packet transmission unit 2035 performs parallel-serial conversion on the response converted into the packet, and transmits the response to the serial bus 300. The parallel-serial conversion operation is the same as the operation of the request packet transmission unit 1032, and thus the description thereof is omitted here. The parallel-serial converted character is transmitted to the receiving side ASIC_A 100 via the serial bus 300 together with the clock.

[Response reception processing]
Next, a response reception process by the first bridge 103 will be described. The response packet receiving unit 1033 receives the character transmitted from the ASIC_B 200 via the serial bus 300, and performs serial-parallel conversion. Since the operation of serial-parallel conversion is the same as that of the request packet receiving unit 2030, description thereof is omitted here.

  The response reception history holding unit 1037 holds transfer attribute information (RespAtrb0 / 1) for at least two past transfers. An example of information held in the response reception history holding unit 1037 is shown in FIG. The response packet inverse conversion unit 1034 performs conversion from a packet performed by an identifier (Type) indicating the type of transfer into a response format to the first bus. Since the detailed description of the identifier is the same as the description of the request transmission process, it is omitted here. If the identifier indicating the packet type indicates a packet to which transfer attribute information (RespAtrb0 / 1) is added, the transfer attribute information (RespAtrb0 / 1) is extracted from the received packet, and is sent to the first bus. Convert to response format. Further, the extracted transfer attribute information (RespAtrb0 / 1) is held in the response reception history holding unit 1037. However, if the number of transfer attribute information (RespAtrb0 / 1) held in the response reception history holding unit 1037 is the maximum holdable number, the oldest transfer attribute information (RespAtrb) held is deleted. . Instead, the received transfer attribute information (RespAtrb0 / 1) is held. On the other hand, if the identifier indicating the packet type is an identifier indicating that the transfer attribute information (RespAtrb0 / 1) is not added, the transfer attribute information (RespAtrb0 / 1) held in the response reception history holding unit 1037. ). For example, if the identifier is “10110”, the transfer attribute information of the combination 3 is referred to. Then, using the referenced transfer attribute information (RespAtrb0 / 1), it is converted into a response format to the first bus. The first bus response transmission unit 1035 transmits the response converted into the response format to the first bus via the first bus 105 to the first bus master that issued the corresponding request.

[AXI]
FIG. 8 shows control signals and address / data / attribute information of an AXI (Advanced Extensible Interface) bus which is a bus protocol used in the integrated circuit.

  The AXI bus protocol has a transfer path called five channels. Each channel has a read address channel carrying a read address, a write address channel carrying a write address, a read data channel carrying a read response / data, a write data channel carrying a write data, and a write response channel carrying a write response. It is. Each channel performs a handshake by a Valid / Ready signal that controls transfer exchange / timing, and performs a series of transfer procedures. In addition to the address and data, which are basic information for data transfer, each channel includes transfer attribute information xBURST indicating transfer type, xLEN indicating transfer length, xLOC indicating atomic transfer, and cache control information. XCACHE indicating transfer security information, xPROT indicating transfer data width, xSIZE indicating transfer priority, xQOS indicating transfer priority, xBURST indicating a transfer area section, and xUSER signal carrying arbitrary user information are defined.

[History holding section]
The history holding unit (1036, 2037, 2036, 1038) does not hold the same attribute information as already held, and when attribute information different from the already held attribute information is received (from the packet conversion unit) This corresponds to the case where the attribute information received from the bus is not replaced with the identifier). When adding and holding, the oldest held one is rewritten to add. Whether it is already held as a history is determined on the transmission side, and on the receiving side, it is determined by the identifier of the packet, whether it is held, and what information matches if it is held.

  FIG. 9 shows a history table held by each transmission history holding unit (1036, 2037) and reception history holding unit (2036, 1038). The history table holds a combination of a plurality of attribute information. Although not shown, it is preferable to store the information stored in each entry in association with information that indicates the most recent transfer packet.

  The attribute information of the first bus (AXI) and the second bus (AXI) includes an exclusive control attribute (LOCK), a cache attribute (CACHE), a security attribute (PORT), a data size (SIZE), a request type (BURST), It has a transmission source (ID) and the like.

  The exclusive control attribute (LOCK) indicates whether or not the transfer is performed after performing a procedure for exclusively using the system bus on the receiving device side. As an exclusive control attribute (LOCK) signal, a “Lock” bit indicating whether or not to perform a bus lock transfer, and an “Exclusive” bit indicating whether or not to perform an exclusive transfer for improving system performance, respectively. It is expressed by 1 bit.

  The cache attribute (CACHE) indicates whether or not the receiving apparatus permits buffering of transfer contents in the route to the data transfer destination. 4 bits are allocated to the cache attribute (CACHE), a bit indicating whether or not caching is possible, a bit indicating whether or not buffering is possible, and a field (2 that indicates to the cache system itself such as WriteThrough and WriteBack when a cache miss occurs Bit).

  The security attribute indicates whether or not the transfer is performed after performing a procedure so that data is received by a slave having a high security level.

  The request type (BURST) indicates the type of transfer, and is expressed by encoding three of INCR (continuous address transfer) / FIXED (address fixed) / WRAP (addressing at the time of cache miss) into 2 bits.

  The data size indicates that data transfer is performed in the unit indicated by the data size. For example, even if the physical data width is 128 bits, 8 bits / 16 bits /. . This indicates which data width is used for transfer, such as / 128 bits. In order to simplify the description, an example in which the transmission history holding unit holds a table has been described. However, it is not necessary to use a table format if the information is equivalent.

  As described above, in the first embodiment, when generating a request packet, the first bridge 103 refers to transfer attribute information (ReqAtrb0 / 1) of not only the previous transfer but also the previous several transfers. Then, the referred transfer attribute information (ReqAtrb0 / 1) is compared with the transfer attribute information (RespAtrb0 / 1) of the transfer to be transferred from now on. When the comparison results match, the transfer attribute information (ReqAtrb0 / 1) is not added to the packet, thereby reducing the number of characters required for transfer. With such a configuration, the transfer attribute information (ReqAtrb0 / 1) does not match the previous transfer, but the transfer attribute information (RespAtrb0 / 1) matches the previous or third transfer. Even in this case, it is possible to reduce the number of characters required for transfer and increase the transfer efficiency.

  On the other hand, when generating the response packet, the second bridge 203 of the present embodiment refers to transfer attribute information (RespAtrb0 / 1) of not only the previous transfer but also the previous few transfers. Then, the referred transfer attribute information (RespAtrb0 / 1) is compared with the transfer attribute information (RespAtrb0 / 1) of the transfer to be transferred from now on. When the comparison results match, the transfer attribute information (RespAtrb0 / 1) is not added to the packet, thereby reducing the number of characters required for transfer. With such a configuration, the transfer attribute information (RespAtrb0 / 1) does not match the previous transfer, but the transfer attribute information (RespAtrb0 / 1) matches the previous or third transfer. Even in this case, it is possible to reduce the number of characters required for transfer and increase the transfer efficiency.

  FIG. 6A shows the number of cycles required for request packet transmission in the conventional example, and FIG. 6B shows the number of cycles required for request packet transmission in the present invention. The numbers in the figure indicate the number of cycles required for transfer. In the example of FIGS. 6A and 6B, requests from the first bus master A101 (A1 to A4 in the figure) and requests from the first bus master B102 (B1 to B4 in the figure) are alternately switched to the first bridge 103. It is an example transmitted to. All transfers are assumed to be 64-bit single write transfers. In this example, it is assumed that the transfer attribute information (ReqAtrb0 / 1) issued from the first bus master A101 is different from the transfer attribute information (ReqAtrb0 / 1) issued from the first bus master B102. In the example of FIG. 6 (a), characters are not reduced at the time of packet generation, and all packets from each master are composed of a 3-character header and 3-character data. Become. Therefore, 6 (number of characters) * 4 (number of transfers per master) * 2 (number of masters) = 48 characters are required to perform four write transfers from each master. Since the transfer of each character takes 34 cycles, 48 * 34 = 1632 cycles are required for the transfer of the conventional example. According to the present invention, characters are reduced when generating the second and subsequent packets from each master. Therefore, while the number of characters in a packet that is not subjected to character reduction is 6 characters, the number of characters transferred from the second transfer onward from each master can be reduced to 5 characters. Therefore, the number of characters required to perform four write transfers from each master is 6 (number of characters in the first transfer) * 2 (number of masters) +5 (number of characters after the second transfer) * 3 (from each master) Total number of transfers-1) * 2 (number of masters) = 42 characters. Since the transfer of each character takes 34 cycles, the transfer of the present invention requires 42 * 34 = 1428 cycles. Since 1632 cycles are required for the same transfer in the conventional example, the present invention can reduce the number of cycles required for 204 cycle transfer compared to the conventional example.

  In the present embodiment, a past transfer number having the same transfer attribute information in Type is assigned. However, by assigning a transfer number to the Reserved area in the first character, the reference number of the past transfer attribute information is obtained. May increase.

<Embodiment 2>
The request transmission history holding unit 1036 and the request reception history holding unit 2036 described in the first embodiment preferentially hold transfer attribute information (ReqAtrb0 / 1) of a new transfer. However, the request transmission history holding unit 1036 and the request reception history holding unit 2036 preferentially hold the transfer attribute information (ReqAtrb0 / 1) of the transfer having a large number of matches as a result of the comparison of the attribute information at the time of transfer. (Transfer attribute information with a large number of matches corresponds to transfer attribute information with a large number of times assigned to a packet, and in this case, it is replaced with transfer attribute information with a small number of times given to a packet.) . Further, the response transmission history holding unit 2037 and the response reception history holding unit 1037 described in the first embodiment preferentially hold transfer attribute information (RespAtrb0 / 1) of a new transfer. However, the response transmission history holding unit 2037 and the response reception history holding unit 1037 preferentially hold the transfer attribute information (RespAtrb0 / 1) of the transfer having a large number of matches as a result of the comparison of the attribute information when performing the transfer. It can also be configured. In the following description, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and descriptions of components that are not functionally changed are omitted.

[Request transmission processing]
The request transmission history holding unit 1036 holds an identifier indicating how many times the transfer and transfer attribute information (ReqAtrb0 / 1) match the request transmission history holding unit 1036 of the first embodiment. The request packet conversion unit 1031 refers to the past transfer attribute information (ReqAtrb0 / 1) held in the request transmission history holding unit 1036 when converting a request from the first bus into a packet, and matches Make a comparison. Depending on the comparison result, conversion into a different packet is performed. If the comparison results do not match, a packet is generated as in the first embodiment, and the transfer attribute information (ReqAtrb0 / 1) is held in the request transmission history holding unit 1036. However, if the number of transfer attribute information (ReqAtrb0 / 1) held in the request transmission history holding unit 1036 is the maximum number that can be held, the number of matches held in the request transmission history holding unit 1036 is indicated. Refers to an identifier. As a result of the reference, the transfer attribute information (ReqAtrb0 / 1) having the smallest number of matches is deleted. Instead, transfer attribute information (ReqAtrb0 / 1) to be transferred is held. On the other hand, if the comparison results match, a packet is generated as in the first embodiment. Further, the value of the identifier indicating the number of matches of the matched transfer attribute information (ReqAtrb0 / 1) held in the request transmission history holding unit 1036 is incremented by one.

[Request reception processing]
The request reception history holding unit 2036 holds an identifier indicating how many times the transfer and transfer attribute information (ReqAtrb0 / 1) match the request reception history holding unit 2036 of the first embodiment. The request packet reverse conversion unit 2031 performs conversion from a packet to a request format to the second bus by an identifier (Type) indicating the type of transfer. If the identifier indicating the packet type indicates a packet to which transfer attribute information (ReqAtrb0 / 1) is added, it is converted into a request format to the second bus as in the first embodiment. Further, the extracted transfer attribute information (ReqAtrb0 / 1) is held in the request reception history holding unit 2036. However, if the number of transfer attribute information (ReqAtrb0 / 1) held in the request reception history holding unit 2036 is the maximum number that can be held, the number of matches held in the request reception history holding unit 2036 is indicated. Refers to an identifier. As a result of the reference, the transfer attribute information (ReqAtrb0 / 1) having the smallest number of matches is deleted. Instead, the received transfer attribute information (ReqAtrb0 / 1) is held. On the other hand, if the identifier indicating the type of packet is an identifier indicating that transfer attribute information (ReqAtrb0 / 1) is not added, it is converted into a request format to the second bus as in the first embodiment. Further, the identifier value indicating the number of matches of the matched transfer attribute information (ReqAtrb0 / 1) held in the request reception history holding unit 2036 is incremented by one.

[Response transmission processing]
The response transmission history holding unit 2037 holds an identifier indicating how many times the transfer and transfer attribute information (RespAtrb0 / 1) match the response transmission history holding unit 2037 of the first embodiment. The response packet conversion unit 2034 refers to the past transfer attribute information (RespAtrb0 / 1) held in the response transmission history holding unit 2037 when converting the response from the second bus into a packet, and matches Search for any. Depending on the comparison result, conversion into a different packet is performed. If the comparison results do not match, a packet is generated as in the first embodiment, and the transfer attribute information (RespAtrb0 / 1) is held in the response transmission history holding unit 2037. However, if the number of transfer attribute information (RespAtrb0 / 1) held in the response transmission history holding unit 2037 is the maximum number that can be held, the number of matches held in the response transmission history holding unit 2037 is indicated. Refers to an identifier. As a result of the reference, the transfer attribute information (RespAtrb0 / 1) having the smallest number of matches is deleted. Instead, transfer attribute information (RespAtrb0 / 1) to be transferred is held. If the comparison results match, a packet is generated as in the first embodiment. Further, the identifier value indicating the number of matches of the matched transfer attribute information (RespAtrb0 / 1) held in the response transmission history holding unit 2037 is incremented by one.

[Response reception processing]
The response reception history holding unit 1037 holds an identifier indicating how many times the transfer and transfer attribute information (RespAtrb0 / 1) match the response reception history holding unit 1037 of the first embodiment. The response packet inverse conversion unit 1034 performs conversion from a packet to a response format to the first bus by an identifier (Type) indicating the type of transfer. If the identifier indicating the packet type indicates a packet to which transfer attribute information (RespAtrb0 / 1) is added, it is converted into a response format to the first bus as in the first embodiment. Further, the extracted transfer attribute information (RespAtrb0 / 1) is held in the response reception history holding unit 1037. However, if the number of transfer attribute information (RespAtrb0 / 1) held in the response reception history holding unit 1037 is the maximum number that can be held, the number of matches held in the response reception history holding unit 1037 is indicated. Refers to an identifier. As a result of the reference, the transfer attribute information (RespAtrb0 / 1) having the smallest number of matches is deleted. Instead, the received transfer attribute information (RespAtrb0 / 1) is held. On the other hand, if the identifier indicating the type of packet is an identifier indicating that transfer attribute information (RespAtrb0 / 1) is not added, it is converted into a response format to the first bus as in the first embodiment. Further, the identifier value indicating the number of matches of the matched transfer attribute information (RespAtrb0 / 1) held in the response reception history holding unit 1037 is incremented by one.

  As described above, according to the present embodiment, transfer information can be compressed more efficiently than in the first embodiment.

  In the above-described embodiment, data transfer between integrated circuits (between chips and modules) has been described. However, the present invention can also be applied to data transfer within the same integrated circuit (same chip, same module). .

  However, transfer between chips has a lower ability to transfer data than transfer within a chip, and is likely to be a bottleneck of the system. In the transfer within the chip, signal lines physically exist for “attribute information”, “address”, and “data”, respectively, and can be transferred simultaneously and in parallel. On the other hand, when transferring between chips, a common signal line is used to reduce the cost of the product (since the IO pins of the chip cause an increase in cost), and transfer is performed in time series. The improvement in transfer efficiency according to the embodiment is remarkable as compared with the transfer in the chip.

  Furthermore, if it is known in advance that there is a part that is known not to change for the upper or lower address, the address that does not change with the attribute information is included in the attribute information table by including the upper (or lower) address information. May be configured such that a part of them (upper or lower several bits) is compressed together. For example, in consideration of the characteristics of the software address map and the bus standard, when accessing a certain module, the upper 4 bits are always fixed to “0000”. In that case, if the upper address comparison value is entered in the table, the data transfer efficiency is further improved by the number of address bits without fluctuation (the same applies to the lower address). In this case, when replacing an unchanged address part with an identifier, it may be replaced only by confirming that the combination of attribute information matches.

  In the above-described embodiment, if the combination of attribute information does not match what is held, only an identifier indicating that the combination does not match is added. The address portion that is not to be replaced may be replaced. In that case, the composite side may be provided with a configuration for adding an address portion that does not always change.

  In the above-described embodiment, AXI has been described as the protocol used for the first bus 105, the second bus 205 in FIG. 1, or the bus 909 and the bus 910 in FIG. 7, but the present invention provides data, address, and attribute information. If the protocol is combined and transferred, the effect can be exhibited widely. Note that the present invention can be applied even when a plurality of transfer contents are expressed as a plurality of bits as one attribute information.

Claims (12)

Holding means for holding a plurality of packet attribute information in association with the first identifier;
Receiving means for receiving a transfer request including attribute information indicating a type of data transfer;
When the attribute information received by the receiving unit matches the attribute information held by the holding unit, the attribute information received by the receiving unit matches the attribute information held by the holding unit. A data transfer apparatus comprising: a transmission unit that includes one identifier in a packet instead of the attribute information received by the reception unit and transmits the packet.   2. The data transfer apparatus according to claim 1, wherein the transmission unit transmits a second identifier indicating whether or not the first identifier is included, added to a transfer request.   When the transmission means transmits a transfer request including a first identifier indicating that the attribute information of the transfer request received by the reception means does not match any attribute information held by the holding means, the transmission means The data transfer apparatus according to claim 1, wherein the attribute information included is held in the holding unit.   If the attribute information of the transfer request received by the receiving means does not match the attribute information held in the holding means, the sending means receives the second identifier indicating that they do not match by the receiving means. 4. The data transfer apparatus according to claim 1, wherein the data transfer apparatus transmits the packet together with the attribute information.   5. The receiving device according to claim 1, wherein the receiving unit receives a transfer request via the first bus, and the transmitting unit transmits the packet after converting the attribute information to conform to the format of the second bus. 2. A data transfer apparatus according to claim 1. Receiving means for receiving a transfer request including the first identifier;
Holding means for holding a plurality of attribute information of packets received in the past in association with the first identifier;
Transmitting means for transmitting attribute information corresponding to the first identifier received by the receiving means out of the attribute information held by the holding means in a packet instead of the identifier received by the receiving means. A data transfer device.   The data transfer apparatus according to claim 6, wherein the receiving unit further receives a second identifier indicating whether or not the first identifier is included.   8. The data transfer apparatus according to claim 6, wherein the receiving unit receives attribute information that has not been replaced with the first identifier, and causes the holding unit to hold the attribute information.   When the holding means receives attribute information to be further held in a state where a predetermined number of pieces of attribute information of packets transmitted in the past are held, the holding means replaces the oldest held attribute information with the attribute information to be held. The data transfer device according to claim 1, wherein the data transfer device is a data transfer device.   When the holding means receives attribute information to be further held in a state where a predetermined number of pieces of attribute information of packets transmitted in the past are held, the attribute having a small number of times given to the packet among the attribute information held by the holding means The data transfer device according to claim 1, wherein the data transfer device is replaced with information. A data transfer method by a data transfer apparatus, comprising: a holding unit that holds a plurality of packet attribute information in association with a first identifier; and a receiving unit that receives a transfer request including attribute information indicating a type of data transfer. ,
When the attribute information received by the receiving unit matches the attribute information held by the holding unit, the attribute information received by the receiving unit matches the attribute information held by the holding unit. A data transfer method characterized in that one identifier is included in a packet instead of the attribute information received by the receiving means and transmitted. A data transfer method by a data transfer apparatus comprising: a holding unit that holds a plurality of packet attribute information in association with the first identifier; and a receiving unit that receives a transfer request including the first identifier,
A data transfer method characterized in that attribute information corresponding to a first identifier received by the receiving means among attribute information held by the holding means is included in a packet instead of the identifier received by the receiving means and transmitted. .

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