JP2523167B2 - Command chain controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a command chain control device when a command chain is issued to an input / output control device connected to an information processing device by a bus, and relates to a bus load condition and a bus use of the input / output device. For the purpose of I / O operations being performed at high speed and with stable performance without affecting priority, it is connected to the information processing device via a common bus, and the I / O devices under it are connected according to the instructions of the information processing device. A command chain control device that controls an input / output control device that controls an input / output operation when a command is issued from the information processing device, and means for analyzing a command fetched from the information processing device; If there is a second command that is chained to the first command that was executed, the second command is executed before the processing of the first command is executed. Means for prefetching from the device, means for storing the first and second commands fetched from the information processing device together with a flag indicating whether or not there is a command to chain to the command, and the means for storing the command based on the flag. Means for performing chain processing of all the commands constituting the command chain.

[Industrial applications]

The present invention relates to a command chain device when a command is issued to an input / output control device connected to an information processing device via a bus.

[Conventional technology]

An information processing apparatus is generally equipped with many input / output devices, and an input / output control device is used to control input / output operations between these input / output devices and the information processing device.

FIG. 5 is a principle diagram of an input / output control system using the input / output control device. In the figure, 21 is an information processing device, and 211 is a main memory for storing various commands for input / output control and transfer data. The main memory 211 exemplifies the commands CCW _{31 to} CCW ₃₃ used in the command chain.

Reference numeral 22 denotes an input / output channel, which is an interface unit that receives commands issued from the information processing device 21 and monitors the state of the input / output control device.

23 is an input / output control device, which analyzes commands by the microprogram control method, controls the operation unique to the input / output device,
Monitors and starts multiple I / O devices. The I / O channel 22 is provided with the function of adapting to its standard control.

24A to 24N are each input / output device under the input / output control device 23, 25
Is a common bus connecting the I / O channel 22 and the I / O controller 23, and 26 is the I / O controller 23 and each of the I / O devices 24 under it.
Input / output bus for connecting A to 24N.

Next, the input / output control operation of FIG. 5 will be described. The information processing device 21 issues a command specifying the device number of the access target input / output device (24A) to the input / output channel. The input / output channel 22 passes this command via the bus 25 to the input / output control device 23 controlling the corresponding input / output device 24A.

The input / output control device 23 analyzes the received command, activates the designated input / output device 24A, and controls the input / output operation such as writing or reading designated by the command.

This input / output operation includes one performed by one command and one performed by a chaining method performed by a plurality of commands.

In the input / output operation performed by one command, the information processing device 21 issues a basic command. FIG. 4 (A) shows an example of the format of the basic command (indicated by COW ₁₀ ). In the figure, the CC section is a command code section, in which the type of command such as writing or reading is set. The control flag part has a chain data flag (hereinafter, referred to as CDF) for instructing a data chain,
Various control flags such as a chain command flag (hereinafter, referred to as CCF) for instructing a command chain and a termination flag for instructing the end of the command are set. The address and data length of the transfer data in the main memory 211 are set in the data section.

When the input / output control device 23 analyzes the command code part and control flag part of the command CCW ₁₀ received from the input / output channel 22 and determines that the command CCW ₁₀ is the basic form, the address and data length designated by the data part According to the above, data transfer between the main memory 211 and the input / output device 24A is controlled. When the input / output operation designated by the command CCW ₁₀ is completed, the input / output controller 23 notifies the input / output channel 22 of the end of the command processing. The input / output channel 22 further notifies the information processing device 21 of this processing end, and ends the processing of the command notified from the information processing device 21.

Next, in the input / output operation by the chaining method, when the input / output operation by one command is completed, the input / output control device 23 does not perform an input / output interrupt to the information processing device 21 and outputs the information via the input / output channel 22. The next command is fetched from the main memory 211, and the input / output operation instructed by the command is performed. This chaining method includes a method in which (a) data chain, (b) command chain, and (c) both are mixed. Hereinafter, these processing methods will be briefly described.

(A) Data chain In the data chain, as shown in FIG. 4 (B), a plurality of commands of the same type (indicated by CCW ₂₁ , CCW ₂₂ , CCW _23, etc.)
Is issued and data is transferred to and from a plurality of areas on the main memory 211 by one input / output operation. That is,
These chained commands CCW _{21 to} CCW ₂₃ are processed as one command.

The commands CCW _{21 to} CCW _{23 have} the same format as the basic command CCW ₁₀ , but the chain data flag CDF in the control flag portion is set to "1". Also, 2
The command codes of the second and subsequent commands CCW ₂₂ and CCW ₂₃ are ignored because they match the command code of the _first command CCW ₁ .

The input / output control device 23 analyzes the command code part CC and the control flag part of the first command CCW ₂₁ received from the input / output channel 22, and because the chain data flag CDF ₂₁ is “1”, the data chain processing is performed. Detect that there is.

In the case of the data chain, when the input / output processing instructed by the command code section CC of the data in the address section instructed by the data section of the first command CCW ₂₁ is completed, the address instructed by the data section of the next command CCW ₂₂ For the data in the area, the same input / output device as the first command is performed. Chain data flag CDF ₂₂ of the second command CCW ₂₂ is when the "1", when a predetermined input operation for the data of the address area to instruct the data portion of the command CCW ₂₂ is completed, the next third Command CCW ₂₃
The same input / output processing is performed on the data in the address area designated by the data section of the above. The termination flag in the control flag part of the command CCW ₂₃ is set to ON, and the data chain is instructed to be terminated by the command CCW ₂₃ .

When the predetermined input / output processing for all chain data is completed, the input / output controller 23 sets the input / output channel 22.
Notify the end of command processing to. I / O channel 22
Further notifies the information processing device 21 of the end of the processing, and ends the processing of the data chain notified by the information processing device 21.

(B) Command chain In the command chain, as shown in FIG. 4 (c), a plurality of commands (indicated by CCW ₃₁ , CCW ₃₂ , CCW _33, etc.) are issued in a chain, and the command specified by one command is issued. When the output operation ends, the next command is automatically fetched from the main memory 211 without causing an input / output interrupt to the information processing device 21, and a new input / output operation instructed by the command is performed.

The commands CCW _{31 to} CCW ₃₃ have the same format as the basic command CCW ₁₀ , but the chain command flag CCF in the control flag section is set to "1" and the chain data flag CDF is set to "0". .

The input / output control device 23 analyzes the command code portion CC and the control flag portion of the first command CCW ₃₁ received from the input / output channel 22, and outputs the chain command flag CCF.
_{Since 31} is "1" and the chain data flag CDF is "0", it is detected that the command chain process is in progress.

In the case of the command chain, the input / output operation of each command is performed in the same manner as the basic type command CCW ₁₀ , but the commands CCW _{31 to} CCW ₃₃ are consecutive in the form of a chain as shown in FIG. Since the addresses are arranged on the main memory 211, the addresses of the second and subsequent commands on the main memory 211 are automatically obtained sequentially from the address of the first command CCW ₃₁ .

Therefore, when the input / output processing of the first command CCW ₃₁ is completed, the input / output device 23 does not cause an input / output interrupt to the information processing device 21 and executes the next second command CCW ₃₂ obtained internally. Main memory 2 via I / O channel 22
It fetches from 11 and controls the new input / output operation instructed by the command code section CC of the command CCW ₃₂ .

Similarly, when the input / output processing of the command CCW ₃₂ is completed, the next third command CCW ₃₃ is fetched from the main memory 211 and the input / output operation instructed by the command CCW ₃₃ is controlled. The termination flag in the control flag part of the command CCW ₃₃ is set to ON, and it is instructed that the command chain is terminated by the command CCW ₃₃ .

When the predetermined I / O processing for all chain commands is completed, the I / O controller 23 determines the I / O channel.
Notify 22 of the end of command processing. I / O channel 22
Further informs the information processing device 21 of the end of the processing, and ends the processing of the command chain notified by the information processing device 21.

(C) When the data chain and the command chain are mixed, in this case, as shown in FIG. 4 (D), the data chain (CCW ₄₁ and CCW ₄₂ ) is regarded as one command, and this and the next command ( CCW ₄₃ ) constitutes the command chain.

For the command parts CCW ₄₁ and CCW ₄₂ of the data chain, the data chain processing is performed in the same manner as (a) above, and for the subsequent command CCW ₄₄ , the above (b)
Command chain processing is performed in the same manner as.

In each command processing described above, the information processing device
When the I / O channel 22 is started by giving an I / O command to it, the I / O channel 22 is released from I / O processing after that, and other processing is performed until the I / O processing ends and an I / O interrupt comes up from the I / O channel 22. Can be executed.

In the basic command CCW ₁₀ , an input / output interrupt is issued from the input / output channel 22 to the information processing device 21 each time the processing of each command is completed. The entire data chain is treated as one command, and an input / output interrupt is issued to the information processing device 21 after the input / output processing of all data is completed. In the command chain, the next command is fetched from the main memory 211 each time the processing of each command ends, but the input / output interrupt to the information processing device 21 is performed after the processing of all commands is completed. An input / output interrupt is issued to the information processing device 21 after the processing of both the data chain and the command chain is completed.

By thus performing the data chain and the command chain, the input / output processing can be efficiently performed, and the number of input / output interrupts is reduced, which reduces the load on the information processing device and improves the processing efficiency. Can be made.

[Problems to be Solved by the Invention]

The input / output processing between the information processing device 21 and each of the input / output devices 24A to 24N can be efficiently performed by the data chain or the command chain as described above.

However, since the information processing device 21 and each of the input / output devices 24A to 24N are connected via the common bus 25, if the number of input / output devices connected to the bus 25 increases, the bus load becomes a problem. In particular, since a large-sized information processing device is equipped with an extremely large number of input / output devices, the problem of bus overload becomes significant.

Therefore, in order to prevent the bus from becoming overloaded, priority is given to the bus usage according to the type of normal I / O device, and when the bus load becomes high due to contention of I / O interrupts, priority is given to it. Highly frequent I / O devices are given priority to use the bus.

However, when the priority is given to the bus use of the input / output device in this way, when the load on the bus is high, the input / output device with a low priority cannot use the bus.
There was a problem that the input / output processing was delayed and the input / output processing efficiency was affected by the load condition of the bus, and stable performance could not be obtained.

In the case of the data chain, the entire command is considered to be one command, and the contents of the input / output processing performed during the data chain processing does not change (for example, write processing and read processing), so the bus cannot be used and the next Even if the data fetch is delayed, the completion of the predetermined input / output processing will be delayed, but the input / output processing itself does not usually result in an error.

On the other hand, in the case of the command chain, when the processing of one command is completed and the fetch of the next command is delayed because the bus cannot be used, the next command processing cannot be executed, so the overall processing is delayed. As well,
The command chain may not be processed normally. For example, in the case of an input / output device such as a communication control device that exchanges data with the other party, if the next command receives data from the other party, the data from the other party will be delayed if the fetch of the next command is delayed. There is a problem that it becomes impossible to receive.

According to the present invention, when the command to the input / output control device is a command chain, high-speed and stable input / output operation is performed without being affected by the load status of the bus and the bus use priority of the input / output device. An object of the present invention is to provide an improved command chain control device.

[Means for solving the problem]

Means adopted by the present invention to solve the above problems will be described with reference to the principle diagram of FIG.

In FIG. 1, 11 is an information processing apparatus, and 111 is a main memory for storing various commands for input / output control and transfer data. In the main memory 111, CCW ₃₁ , CCW _{32 and the} like are channel command words, which are continuously arranged in a chain format on the main memory 111. CAW is the channel address word, the first CCW
The address on the main memory 111 of (CCW _{31 in} the case of command chain) is designated. In the command chain, if the address of the first command CCW ₃₁ is designated, the address on the main memory 111 of each CCW after the second command CCW ₃₂ is
It is automatically obtained from the address of the first command CCW ₃₁ and the length of each CCW.

Reference numeral 12 is an input / output control device, which analyzes the input commands by microprogram control, controls the operation peculiar to the input / output device, and monitors and starts a plurality of input / output devices. If there is an I / O channel, match standard I / O channel controls.

The inside of the input / output control device 12 shows the software structure of the input / output control device 12. Reference numeral 120 denotes a memory in the input / output control device (hereinafter referred to as IOC memory), which internally has a microprogram area 121, a prefetch command area 122,
A chain instruction flag area 123 and a control area 124 are provided. The micro program area 121 stores a micro program MCP for performing micro program control.
The prefetch command area 122 stores each command prefetched from the main memory 111. The chain instruction flag area 123 has a chain instruction flag (indicated by CIF).
Is stored. The chain instruction flag CIF is provided corresponding to each prefetch command, and is set to ON when chaining to the prefetch command, and cleared to OFF when there is no prefetch command. Each information for operating the input / output device is set in the control area 124.

13A to 13N are input / output devices under the input / output control device 12. Reference numeral 14 is a common bus that connects the information processing device 11 and the input / output control device 12, and 15 is an input / output bus that connects the input / output control device 12 and the subordinate input / output devices 13A to 13N.

Reference numeral 16 denotes an input / output channel, which is an interface unit that receives commands issued from the information processing device 11 and monitors the state of the input / output control device 12. However, the input / output channel 16 is not essential, and may be performed by the information processing device 11.

The present invention is implemented by the system described above and is configured as follows.

That is, to the input / output control device 12 which is connected to the information processing device 11 by the common bus 14 and controls the input / output operation performed by each of the subordinate input / output devices 13A to 13N by microprogram control according to the instruction of the information processing device 11. In the command chain control device when a command is issued from the information processing device 11, when there is a means for analyzing the command fetched from the information processing device and a second command chained to the analyzed first command. Means for prefetching the second command from the information processing apparatus before the execution of the processing of the first command, and a command for chaining the first and second commands fetched from the information processing apparatus to the command. Means for storing together with a flag for instructing the presence or absence of the command chain, and the stored command chain based on the flag. And means for performing chain processing of all commands to configure.

[Work]

The microprogram MCP (in the microprogram area 121) of the input / output control device 12 analyzes the first command (indicated by CCW ₃₁ ) fetched from the information processing device 11 via the bus 14 (to analyze the command, The microprocessor of the input / output control device 11 (not shown) performs this according to a micro program, but for simplicity, it will be referred to as above).

When there is a chaining command in the first command,
That is, in the case of the command chain, the first command processing execution is reserved, and the microprogram MCP prefetches the next command (indicated by CCW ₃₂ ) from the main memory 111. The second prefetched command CCW ₃₂ is
It is stored at a predetermined position in the prefetch command area 122 together with the first command CCW ₃₁ .

At the same time, the chain instruction flag (indicated by CIF ₃₁ ) corresponding to the first command CCW ₃₁ in the chain instruction area 123 is set to ON.

The microprogram MCP analyzes the prefetched second command CCW ₃₂ and detects the presence or absence of the next chained command.

When there is a command to be chained next, the third command (CCW ₃₃ ) to be chained is prefetched from the main memory 111 and stored in a predetermined position of the prefetch command area 122. Along with that, the chain instruction area 123
The chain instruction flag (indicated by CIF ₃₂ ) corresponding to the second command CCW ₃₂ in the above is set to ON.

Similarly, the commands to be chained are sequentially prefetched and stored in a predetermined position of the prefetch command area 122, and the corresponding chain instruction flag CIF is set to ON. Since there is no chaining command in the last command of the chain commands, the corresponding chain instruction flag CIF is cleared to off.

When all the commands in the chain have been prefetched, the microprogram starts the command chain process.

First command CCW ₃₁ prefetch command area 122
To retrieve and execute the command processing. command
In the result of termination of CCW ₃₁ , its chain instruction flag CIF ₃₁
When it is detected that the command is set to ON, the command CCW _{31 to} be terminated is confirmed not to be in error termination, and then the prefetch command area
The second command CCW ₃₂ is fetched from the predetermined position 122 and its processing is executed.

Similarly, when the chain instruction flag CIF _3j is turned on in the termination processing of one command CCW _3j ,
The next command is fetched from the prefetch command area 122 and executed.

When a command CCW _3j of chain indication flag CIF _3j is cleared off, it recognizes that the command chain is terminated, and terminates the command chain processing notifies the processing termination to the information processing apparatus 11.

As described above, the command chain is executed after prefetching all the commands that make up the command chain into the I / O controller, so the next command is fetched via the bus each time one command is completed. The command chain can be executed in the I / O controller without needing to do so.

As a result, the command chain in the I / O controller can be executed, so high-speed and stable I / O operations can be performed without being affected by the load status of the bus and the priority of bus usage of the I / O device. it can.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a command prefetch processing flowchart of one embodiment of the present invention, and FIG. 3 is a command chain processing flowchart of the same embodiment. The formats of the implementation system of FIG. 1 and the commands of FIG. 4 are as described above. The implementation system of FIG. 1 is used as an implementation system of an embodiment of the present invention.

Hereinafter, as shown in FIG. 4 (D), the command CCW
The operation of one embodiment of the present invention will be described by exemplifying a case where ₄₁ and CCW _{42 form a} data chain, and this and the next command CCW ₄₃ form a command chain.

(A) Command Prefetch Process The command prefetch process of the embodiment will be described with reference to the command prefetch process of FIG. 2 and the processing steps thereof. Unless otherwise specified, the following processes are controlled and executed by the microprogram MCP in the microprogram area 121.

Processing S ₁₁ , S _{12 The} information processing device 11 is an input / output device (13
A SIO (start I / O) instruction for activating (A) is issued to the I / O channel 16 (process S ₁₁ ). I / O channel 16
Confirms that the input / output control device 12 controlling the instructed input / output device 13A is in the usable state, the main memory 11
Remove the channel address word CAW output devices 13A located above 1 sends to the output control unit 12 (processing S _12).

Process S _{13 The I} / O control process 12 of the microprogram MCP uses the channel address word CAW received from the I / O channel 16 as the first command (channel command word CCW ₄₁ , fourth command) for instructing the I / O operation content of the I / O device 13. When the address on the main memory 111 of FIG. (D) is obtained, a command CCW ₄₁ (not shown) is fetched from the main memory 111 via the bus 14 according to this address, and the prefetch command area 122
It is stored in a predetermined position inside.

Process S ₁₄ , S ₁₅ , S ₁₆ The microprogram MCP of the I / O controller 12 analyzes the control flag part of the fetched command CCW ₄₁ (process S _14
14 ), first, determine whether it is a data chain (process
S ₁₅ ).

When the chain data flag (indicated by CDF ₄₁ ) that indicates the presence or absence of the data chain is turned on and it is determined to be the data chain, the example of the command CCW ₄₁ is reserved and the next command CCW ₄₂ that forms the data chain is set. Prefetch (process S ₁₆ ). This prefetched command CCW
The control flag portion of ₄₂ is analyzed, and it is determined from the chain data flag (indicated by CDF ₄₂ ) whether it is a data chain (processes S ₁₄ and S ₁₅ ).

Since the data chain ends at CCW ₄₂ and its CDF ₄₂ has been reset off, it is determined that there is no next command to make up the data chain.

Process S ₁₇ , S ₁₈ , S ₁₉ Command If there is no data chain command in CCW ₄₂ , it is determined whether the command chain is based on the ON / OFF state of the chain command flag (indicated by CDF ₄₂ ) that indicates the presence or absence of the command chain. Yes (process S ₁₇ ).

When the CDF ₄₂ is off, there is no command chain and only the data chain, so the chain instruction flag area 12
The chain instruction flag (indicated by CIF ₄₁ ) corresponding to the command CCW ₄₁ in 3 is cleared to OFF (process S ₁₈ ) and the data chain process is executed. In case of data chain or one command, there is no next command.
S ₂₂ is not performed (S ₁₉ ).

If in the process S _20, S ₂₁ processing S ₁₇ flag CCF ₄₂ command CCW ₄₂ is determined to command chain on-the following command
The CCW ₄₃ is prefetched from the main memory 111 via the bus 14 (process S ₂₀ ) and stored at a predetermined position in the prefetch command area 122 (process S ₂₁ ).

Process S ₂₂ Next, the command C in the chain instruction flag area 123
The chain instruction flag CIF ₄₁ corresponding to CW ₄₁ is set to ON (process S ₂₂ ).

Process S ₁₄ , S ₁₅ ,, S ₁₇ ,, S ₁₈ ,, S _{19 When} process S ₂₂ is finished, the process returns to process S ₁₄ and analyzes the control flag part of the prefetched command CCW ₄₃ (process
S ₁₄ ), it is determined whether the data chain is based on the on / off state of the chain data flag (indicated by CDF ₄₃ ) (process S
₁₅ ). Since the flag CDF ₄₃ is off, it is further determined from the on / off state of the chain command flag (indicated by CCF ₄₃ ) whether it is a command chain (process S ₁₇ ). The flag CCF ₄₃ is off because the command chain ends with the command CCW ₄₃ .

If it is determined that the flag CCF ₄₃ is off and there is no command to chain next, the chain instruction flag (indicated by CIF ₄₃ ) corresponding to the command CCW ₄₃ in the chain instruction flag area 123 is cleared to off (process S ₁₈ ), And the presence / absence of a command chain is further determined (process S ₁₉ ).

Process S _{23 When} the prefetch of all the commands in the command chain is completed, the preparation necessary for executing the command CCW ₄₃ next to the command CCW ₄₁ to be executed first is performed (process S ₂₃ ).
As a result, when the processing of command CCW ₄₁ (that is, the data chain) is completed, the next command CCW
₄₃ processes can be executed.

(B) Command Chain Processing Next, the command chain processing of the embodiment will be described with reference to the command chain processing flowchart of FIG. 3 and the processing steps thereof. The following processes are also controlled and executed by the microprogram MCP in the microprogram area 121 unless otherwise specified.

Processing S ₃₁ , S _{32 When the} above command prefetch processing is completed, the microprogram MCP of the input / output control device 12 fetches the first command CCW ₄₁ and executes the processing (processing
S _31). That is, to start the output device 13A which is specified similarly to the conventional method (process S _32), executes the processing of the command CCW _41. The command CCW ₄₁ constitutes a data chain together with the next command CCW ₄₂ , so that the data chain processing is performed as in the conventional method.

When the processing of the last command CCW ₄₂ of the processing S ₃₃ , S ₃₄ data chain is completed normally, the input / output device 13A notifies the input / output control device 12 that the predetermined operation (data writing, reading, etc.) is completed ( process S _33), the microprogram of the input-output control unit 12 which receives the end notification performs cleanup command to release the output device 13A (processing S _34). When an error occurs during the input / output operation, the input / output device 13A notifies the input / output control device 12 of the error. Upon receiving the error notification, the I / O controller 12 terminates the I / O operation in error.

Processing S ₃₅ , S _{36 When the} command termination processing is completed, the microprogram MCP
Determines the presence or absence of the next command based on the on / off state of the chain instruction flag CIF ₄₁ corresponding to COW ₄₁ in the chain instruction flag area 123 (process S ₃₅ ). In this example, the following command CCW ₄₃ is present and flag CIF ₄₁ is set on.

When the flag CIF ₄₁ is on, the presence / absence of error notification is further determined from the input / output device 13A (process _S36 ).

Process S _{37 If the} input / output operation ends normally and there is no error notification from the input / output device 13A, the microprogram MCP performs command termination processing for the host device (process S ₃₇ ). This notifies the information processing apparatus 11 via the input / output channel 16 of the end of the command, that is, the data chain.

Processing S ₃₈ , S ₃₉ Next, the microprogram MCP fetches the next command CCW ₄₃ from the prefetch command area 122, transfers it to the work area in the control area (processing S ₃₈ ), and executes the start processing of the command CCW _43. Perform (process S ₃₉ ).

Processing S _{31 to} S _{34 and} below, for the following command CCW ₄₃ , the processing S ₃₁ described above
To S ₃₄ is performed, when a predetermined input operation is completed, terminates command processing CCW ₄₃ is performed.

Processing S ₃₅ , S _{40 When the} command termination processing is completed, the microprogram MCP
Determines the presence or absence of the next command from the ON / OFF state of the chain instruction flag CIF ₄₃ corresponding to the command CCW ₄₃ in the chain instruction flag area 123 (process S ₃₅ ). Since this embodiment command chain ends in CCW _43, flag CIF ₄₃ are cleared off by the process S ₁₈ described above.

When the flag CIF ₄₃ is off, further determines whether an error notification from the input operation partner (process S _40).

Processing S ₄₁ , S ₄₂ , S ₄₃ If there is no error notification from the input / output operation partner, the microprogram determines that the input / output operation has completed normally and sets the normal termination notification of the command (processing S ₄₁ ). Bus 1
The normal termination of the command is notified to the I / O channel 16 via 4 (process S ₄₂ ).

The input / output channel 16 further notifies the information processing device 11 of this normal termination, and ends the command chain processing (processing
S ₄₃ ).

Processing S ₃₄ , S ₄₅ , S _{46 When} an error is notified in the above processing S ₃₆ or S ₄₀ , the microprogram MCP of the input / output control device 11
In order to notify the information processing device 11 of the end of the input / output operation due to the error occurrence, an error end notification is set (process _S44 ),
The end of error is notified to the input / output channel 16 via the bus 14 (process _S45 ).

The input / output channel 16 further notifies the information processing device 11 of this error termination, and ends the command chain processing.

The embodiment has been described above in which one command chain is instructed after two data chains, but the same can be done in the case of a data chain and a command chain having more commands than this. it can.
Further, the operation in the case of only the data chain or the command chain, and the operation in the case where there is one command is one operation mode of the above-described embodiment and is clear from the operation description of the embodiment, and therefore the operation description thereof will be omitted. Omit it.

〔The invention's effect〕

As described above, according to the present invention, the following various effects can be obtained.

(1) Since the command chain is executed after prefetching all the commands constituting the command chain into the I / O controller, it is necessary to fetch the next command via the bus each time one command is completed. Instead, the command chain can be executed within the I / O controller.

(2) Since the command chain can be executed in the input / output control device according to the above (1), the input / output is fast and stable in performance without being affected by the load condition of the bus and the priority of bus use of the input / output device. You can take action.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a command fetch processing flowchart of one embodiment of the present invention, FIG. 3 is a command chain processing flowchart of the same embodiment, and FIG. 4 is a basic form and a chain. FIG. 5 is an explanatory diagram of a format of each command of the inning system, and FIG. 5 is an explanatory diagram of a conventional input / output control system. In FIG. 1, 11 ... Information processing device, 111 ... Main memory, 12 ... Input / output control device, 120 ... Input / output control device memory (IOC memory), 121 ... Microprogram area, 122 ... Prefetch command area, 123 ... Chain instruction flag area, 124 ... Control area, 13A to 13N ... Input / output device, 14 ...
… Bus, 15… I / O bus, 16… I / O channel.

Claims (1)

(57) [Claims] 1. A command is sent from an information processing device to an input / output control device which is connected to the information processing device by a common bus and controls input / output operations performed by respective subordinate input / output devices according to an instruction from the information processing device. In the command chain control device that performs control when issued, if there is a unit that analyzes a command fetched from the information processing device and a second command that chains to the analyzed first command, the first command Means for prefetching the second command from the information processing apparatus before execution of command processing, and a flag for instructing the presence or absence of a command for chaining the first and second commands fetched from the information processing apparatus to the command Together with a means for storing all of the commands that make up the stored command chain based on the flag. Command chain control apparatus characterized by comprising means for performing Ein process, the.