JPH0844662A - Information processor - Google Patents

Abstract

PURPOSE:To prevent use efficiency of a bus from being lowered even when there is the bus slave of low-speed processing in a system. CONSTITUTION:When requesting processing to bus slaves S1-S3, bus masters M1-M3 acquire the bus use right and issue processing request commands to the bus slaves and afterwards, a shared bus 1 is released. On the other hand, the bus slaves temporarily store the received commands addressed to them in queues, select any one of them and execute prescribed processing. After the end of processing, an answer command to the bus master of the processing request source is prepared, and a bus using request is issued to a bus arbitrating means 2. Concerning the read request commands continued inside the queue, its arrangement inside the queue is changed so that the higher the request level is set, the faster the command can be processed. Besides, the more the commands are stored in the queue, the higher the request level of the bus slave is set so that the use right of the shared bus 1 can be speedily acquired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information processing device which effectively uses a shared bus.

[0002]

2. Description of the Related Art Conventionally, in an information processing apparatus in which a plurality of bus masters and bus slaves are connected to a shared bus,
When setting the priority of bus usage for each bus master and each bus master transferring data via the shared bus,
A bus arbitration unit that arbitrates the use of the bus based on the above-mentioned priority is widely used.

FIG. 6 is a diagram showing a state in which a bus master and a bus slave are connected to a shared bus. In FIG. 6, 1 is a shared bus, 2 is a bus arbitration means, and M _{1 to} M
₃ is a bus master such as a processor and a DMA (Direct Memory Access) controller, and S _{1 to} S ₃ are memories and I
A bus slave such as an / O (input / output) device. bus·
When the masters M _{1 to} M ₃ transfer data to and from the bus slaves S _{1 to} S ₃ , the masters M _{1 to} M ₃ issue a bus use request in response to a program request, and use the shared bus 1 when a bus use permission is issued. . The bus arbitration means 2 is based on the bus use priority set in each of the bus masters M _{1 to} M ₃ .
To arbitrate bus use request among the respective bus masters M ₁ ~M _3.

For example, if the bus use priorities of the bus masters M _{1 to} M ₃ are high in the order of the bus masters M ₃ , M ₂ , and M ₁ , the bus masters M ₁ and M ₃ will When the bus use requests are issued to the bus arbitration means 2 at the same time, the bus arbitration means 2 gives a bus use permission to the bus master M ₃ . However, if the bus master M ₁ is already using the bus, even if the bus master M ₃ issues a bus use request to the bus arbitration means 2, until the bus master M ₁ releases the shared bus 1. Does not give the bus master M ₃ permission to use the bus. Moreover, the bus master M ₁ releases the shared bus 1 after the reply from the bus slave, for example, when data is read from the bus slave, a read command is sent to the bus slave. rear,
This is when the data was returned from the bus slave.

Therefore, in the case of a bus slave that requires a relatively long time to read data after a data read request is made by the bus master M ₁ , other bus masters M ₂ and M are in the meantime. _{In the case of 3,} the shared bus 1 cannot be used, and the use efficiency of the shared bus 1 is reduced. Especially in the recent situation where the speed difference between the microprocessor and the memory becomes a problem due to the advent of the high-speed microprocessor, such a problem also occurs in the memory.

Therefore, as disclosed in Japanese Patent Laid-Open No. 3-51943, the shared bus 1 is used for a bus slave which requires a relatively long time for processing by dividing the command transmission and the reply to the command. , A technique for performing divided access has been proposed. That is, when the bus master accesses a bus slave that supports split access, the shared bus 1 does not wait for a reply from the bus slave.
Is released, the bus slave acquires the right to use the bus after it becomes ready to respond, and sends a reply to the bus master of the transmission source. If you do this, a bus with a slow response
Other bus masters can communicate with other bus slaves while waiting for a reply from the slave.

[0007]

However, in the above-described conventional technique, when one bus master is executing a divided access, another bus master cannot access another bus slave. However, the bus / slave that is being dividedly accessed cannot be accessed. Therefore, when there are a plurality of slow I / O devices in the system, there is a problem that the number of bus masters to be kept waiting increases and the bus usage efficiency decreases. In particular, in a so-called multiprocessor environment using a plurality of microprocessors, the problem becomes more serious. An object of the present invention is to solve the above problems.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a plurality of bus masters requesting processing, a bus slave executing the processing requested by the bus master, and those buses. In an information processing device having a shared bus that commonly connects a master and a bus / slave, and a bus arbitration unit that arbitrates the right to use the shared bus, when the bus master requests the bus slave for processing. To
A bus use request means for issuing a shared bus use request to the bus arbitration means and a command for requesting processing to the bus slave after acquiring the shared bus use right and releasing the shared bus. The bus / slave comprises a queue for storing received commands and a command for self addressed received from a shared bus in the queue, and a command is issued from the commands stored in the queue. Queue management means for selecting one and sending it to the processing execution portion, and command issuing means for creating a reply command to the processing request source bus master after the processing execution portion has completed processing,
To send a reply command to the processing request source bus master,
A bus use request unit for issuing a shared bus use request to the bus arbitration unit is provided. Further, the bus master, when requesting processing from the bus slave,
The command is issued by designating a request level, and the queue management unit rearranges the order of a plurality of consecutive read request commands among the commands in the queue so that the request level becomes higher. did.
Further, when the queue management unit puts a command in the queue, if the queue is full, the bus slave sends a busy command indicating that to all the bus masters. I decided. Furthermore, the bus slave increases the request level of the shared bus use request as the number of commands accumulated in the queue increases.

[0009]

[Operation] When a bus slave receives a command addressed to itself from the shared bus, the queue management means stores it in the queue. Also, the queue management means selects one from the commands stored in the queue and sends it to the processing execution unit. When the processing of the processing execution unit is completed, the command issuing means creates a reply command to the bus master that issued the processing request. Further, the bus use request means issues a request to use the shared bus to the bus arbitration means in order to send a reply command to the bus master which is the processing request source.

As described above, since the queue for storing the commands is provided in the bus slave, even a bus slave which is processing according to a request from a certain bus master can receive a processing request from another bus master. You can As a result, the bus master does not have to wait until the processing of the bus slave is completed, and the efficiency of use of the bus does not decrease.

Further, the bus master requests
A processing request command including a level is issued, and the queue management unit rearranges the order of a plurality of consecutive read request commands among the commands in the queue so that the request level becomes higher. Therefore, when you have a situation where you want to handle it urgently, high request
By issuing a command with a level, it is possible to give flexibility to the command processing such that the processing can be executed earlier.

Further, if the queue management means sends a busy command to all bus masters when the queue is full when a command is put into the queue, It is possible to prevent the bus master from issuing commands to busy bus slaves unnecessarily to increase bus traffic.

Furthermore, as the number of commands accumulated in the queue increases, the request level of bus usage is increased so that the bus slave with many commands preferentially uses the bus. As a result, the processing proceeds faster, the number of commands accumulated in the queue is reduced accordingly, and the number of stages in the queue can be reduced.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a bus master and a bus slave. Among them, FIG. 1 (a) shows a schematic configuration of a bus master, and FIG.
The schematic structure of a slave is shown. Reference numerals 1, M ₁ , S
₁ corresponds to that of FIG. 6, 3 is instruction executing means, 4, 1
0 is bus use requesting means, 5 and 11 are command issuing means,
Reference numerals 6 and 7 are bus monitoring means, 8 is a queue, 9 is a queue management means, and 12 is a memory.

In the bus master M ₁ , the instruction executing means 3 interprets and executes the program, and the bus slave S
When it is necessary to access _{1 to} S ₃ , the request level is specified according to the urgency of the processing, the bus use requesting means 4 is requested to acquire the right to use the shared bus 1, and the command issuing means 5 is commanded. Request the generation of. When the instruction execution means 3 requests the bus use request means 4 to acquire the use right of the shared bus 1, the bus use request means 4 issues a bus use request signal at a designated request level, and the bus arbitration means 2 (see FIG. 6).
When the bus use permission is obtained from, the command issuing means 5 is notified of it. The command issuing means 5 receives a command generation request from the instruction executing means 3 and generates a command. When a command issuance request is received from the bus use request means 4, the generated command is issued on the shared bus 1. The bus monitoring unit 6 constantly monitors the shared bus 1, and when it determines that the command flowing through the shared bus 1 is addressed to itself, acquires it and sends it to the instruction execution unit 3.

Further, in the bus slave S ₁ , the bus monitoring means 7 constantly monitors the shared bus 1, and when it judges that the command flowing through the shared bus 1 is addressed to itself, acquires it. , And informs it to the queue management means 9. The queue management unit 9 puts the command acquired by the bus monitoring unit 7 into the queue 8 or takes out the read / write processing request command from the queue 8 and issues it to the memory 12 as a processing execution unit. Further, in response to the completion of the processing from the memory 12, a reply command is returned to the bus master which is the processing request source. Request to generate a reply command. Further, the queue management means 9 also rearranges the order of a plurality of consecutive read request commands among the commands in the queue 8 so that the request level becomes higher. Furthermore, the queue management means 9
When the command is put in the queue 8, if the queue 8 is already full, the command issuing means 11 is requested to broadcast the busy command.

The bus use request means 10 issues a bus use request signal when receiving a request for acquiring the right to use the shared bus 1 from the queue management means 9, and the bus arbitration means 2 (see FIG. 6).
When the use permission is obtained from the command issuing unit 11, the command issuing unit 11 is notified of the use permission. At this time, the bus use request signal is issued with a higher request level as the number of commands accumulated in the queue 8 increases. Command issuing means 11
Receives a command generation request from the queue management means 9 and generates a command. Further, when a command issuance request is received from the bus use request means 10, the generated command is issued on the shared bus 1. When the memory 12 receives a read / write request from the queue management means 9, it executes the request, and when the requested processing is completed, it notifies the queue management means 9 together with the data.

The bus arbitration means 2 is a bus master M.
Arbitration of bus use requests from _{1 to} M ₃ and bus slaves S _{1 to} S ₃ is performed based on the above request level. That is, the higher the request level, the more preferentially the use of the shared bus 1 is permitted.

FIG. 2 is a diagram showing a command format. As shown in FIG. 2, the command is its own ID.
It has a field for writing (identifier), a field for writing the ID of the other party, a field for writing read / write, a field for writing the request level, a field for writing the address of the other party, and a field for writing the message. In the message field of the command issued from the bus master, the data to be written is written when writing, and nothing is written when reading. Also, in the message field of the reply command issued from the bus slave,
At the time of reading, the data or error message read from the memory 12 is written. When writing, no command is issued except when an error occurs.

FIG. 3 is a diagram showing an example of the contents of the queue. The received command is stored in the queue 8 as it is. For example, if the queue has a depth of 8 stages as shown in FIG. 3, the first stage of the queue is It is where the commands to be sent to memory 12 are stored, and the eighth stage of the queue is where the commands to be serviced most recently are stored. In addition, this queue 8 has two pointers, one of which is the current pointer that indicates how many commands are currently in the queue, and the other is the most recently entered write. A write pointer indicating the position of the command.

Next, the operation of the present invention will be described. The instruction executing means 3 specifies a request level when the application program requests access to the memory 12,
The bus usage request means 4 is requested to acquire the usage right of the shared bus 1, and the command issuing means 5 is requested to generate a command.
The command issuing means 5 receives a command generation request from the instruction executing means 3 and generates a command including the request level. Then, upon receiving a command issuance request from the bus use request means 4, the generated command is issued on the shared bus 1. After issuing the command, the bus is released without waiting for a reply from the bus master.

On the other hand, on the bus / slave side, when the bus monitoring means 7 receives a command addressed to itself, it notifies the queue management means 9 of it. Queue management means 9 that has received the notification
Then, the following processing is performed. FIG. 4 is a flowchart showing the command storing process of the queue managing means. Step 1 ... bus monitor means 7, the bus master M ₁ ~M
Determine whether or not the command is received from ₃ . Step 2 ... When received, queues 1 to 8
It is checked whether or not the queue 8 is full because the command is entered up to the step. The determination can be made based on whether or not the value of the current pointer is "8". Step 3: If the command is full, the command issuing means 11 is requested to issue a busy command. At that time, "0" which means transmission to all the bus masters on the shared bus 1 is put in the field of the ID of the partner of the command shown in FIG.
Send a message indicating that it is busy in the message field.

Step 4 ... If it is not full in Step 2, the current pointer is incremented. Step 5: The received command is inserted as it is at the position pointed to by the current pointer. Step 6 ... Checks whether the received command is a write command requesting data write to the bus slave. Step 7 ... If the command is a write command, the value of the current pointer is assigned to the write pointer. Step 8 ... Not the write command in Step 6,
If it is a read command requesting data read from the bus slave, the read commands from the current pointer to the write pointer + 1 of the queue 8 are arranged so that the higher the request level, the lower the rank. Change.

In this way, the read commands in the queue 8 are rearranged so that the higher the request level is, the lower the rank is. Therefore, the read commands that are urgent need to be increased by increasing the request level. , Can be run faster. However, such rearrangement is performed only for the read commands from the current pointer of the queue 8 to the write pointer + 1.
The reason is that if the order is rearranged including the write command, for example, the order of writing data to and reading from a certain memory may be interchanged, and erroneous data may be read.

FIG. 5 is a flow chart showing the command execution processing of the queue management means. Step 1 ... Checks whether there is no command in the queue 8 and it is empty. The determination is the current
It can be performed by checking whether the value of the pointer is "0". Step 2 ... If not empty, the memory 12 executes the command in the first stage of the queue. Step 3 ... It is determined whether or not the processing of the memory 12 is completed.

Step 4 ... Upon completion, the command issuing means 11 is requested to generate a reply command to the bus master as the processing request source. This reply command has a format similar to that of FIG. 2, and writes the ID of the bus slave in the field of its own ID, the ID of the bus master of the processing request source in the field of the other party, and read / write. The fields for writing other information, the field for writing the request level, and the field for writing the other party's address are blank. Also, the message field contains the memory 1 when the requested process is read.
Write the data or error message read from 2. If it is a write, a write completion message or error message is written.

Step 5 ... Using the value of the current pointer as the request level, the bus use request means 10 is requested to perform a process for making a request for use of the shared bus 1. Step 6 ... Decrements the values of the current pointer and the write pointer by -1. Step 7 ... Move all the commands in the queue 8 toward the first stage of the queue. Step 8: The command issuing means 11 is requested to issue the busy cancellation command. At this time, all the buses on the shared bus 1 are set in the ID field of the other party of the command shown in FIG.
Enter "0", which means to send to the master,
Send a busy release message in the field. In this embodiment, in order to simplify the processing, regardless of whether or not the busy command is issued, the busy release command is issued every time the processing of one command is executed. However, the busy release command may be issued only after the busy command is issued.

When the bus use request means 10 receives a request from the queue management means 9 to make a use request for the shared bus 1, it issues a bus use request signal, and as a result, a use permission is obtained from the bus arbitration means. When it is given, it is transmitted to the command issuing means 11. The command issuing means 11 receives a command generation request from the queue managing means 9, generates a reply command, and when the bus use request means 10 receives the above notification, issues the generated reply command on the shared bus 1.

In the above embodiment, the bus slave S
_Although the case where the processing execution unit ₁ is the memory 12 is shown, the present invention is not limited to this and is similarly applicable to other bus slaves such as I / O devices.

[0030]

As described above, according to the information processing apparatus of the present invention, since the bus slave is provided with the queue for storing the commands, the bus slave performing the processing in response to a request from a certain bus master. However, it has become possible to receive processing requests from other bus masters.
As a result, the bus master does not have to wait until the processing of the bus slave is completed, and the efficiency of use of the bus no longer decreases.

Further, the bus master requests
The processing request command including the level is issued, and the queue management unit rearranges the order of the portion in which the plurality of read request commands are consecutive in the queue so that the request level becomes higher. Therefore, when an emergency situation arises, command processing can be made flexible by issuing a command with a high request level so that the command can be executed quickly. It became so.

Further, when the queue management means puts a command in the queue, if the queue is full, it broadcasts a busy command. Therefore, it becomes possible to prevent the bus master from issuing a command to the busy bus slaves unnecessarily to increase the bus traffic.

Furthermore, as the number of commands accumulated in the queue increases, the request level for bus usage is increased. Therefore, in a bus / slave where a large number of commands have accumulated, the bus can be used preferentially and processing will proceed faster, the number of commands accumulated in the queue will decrease correspondingly, and the number of queue stages will also be reduced. .

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a bus master and a bus slave.

[Figure 2] Diagram showing command format

FIG. 3 is a diagram showing an example of the contents of a queue.

FIG. 4 is a flowchart showing a command storing process of a queue managing means.

FIG. 5 is a flowchart showing command execution processing of queue management means.

FIG. 6 is a diagram showing a state in which a bus master and a bus slave are connected to a shared bus.

[Explanation of symbols]

1 ... Shared bus, 2 ... Bus arbitration means, 3 ... Instruction execution means,
4,10 ... bus request means, 5,11 ... command issuing unit, 6,7 ... bus monitor means, 8 ... queues, 9 ... queue managing unit, 12 ... memory, M ₁ ~M ₃ ... bus master,
S ₁ ~S ₃ ... bus slave

Claims (4)

[Claims] 1. A plurality of bus masters that request processing, a bus slave that executes the processing requested by the bus master, and a shared bus that connects these bus masters and bus slaves in common. In an information processing device having a bus arbitration unit that arbitrates the right to use the shared bus, the bus master, when requesting processing from the bus slave,
A bus use request means for issuing a shared bus use request to the bus arbitration means, and a command for requesting processing to the bus slave after acquiring the shared bus use right, and releasing the shared bus. The bus / slave comprises a queue for storing received commands and a command addressed to itself received from a shared bus in the queue, and a command is issued from the commands stored in the queue. Queue management means for selecting one and sending it to the processing execution portion, and command issuing means for creating a reply command to the bus master of the processing request source after the processing execution portion completes processing,
To send a reply command to the processing request source bus master,
An information processing apparatus, comprising: a bus use request means for issuing a shared bus use request to the bus arbitration means. 2. The bus master issues a command by designating a request level when requesting a process from a bus slave, and the queue managing means issues a plurality of consecutive commands in the queue. The information processing apparatus according to claim 1, wherein the order of the read request commands is rearranged so that the request levels are higher. 3. The bus slave sends a busy command to all the bus masters indicating that the queue is full when the queue management unit puts a command in the queue. The information processing apparatus according to claim 1, wherein the information processing apparatus transmits the information. 4. The information according to claim 1, wherein the bus slave raises the request level of the shared bus use request as the number of commands accumulated in the queue increases. Processing equipment.