JP2525479B2 - Command exclusive control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Table of Contents] Outline Industrial field of application Conventional technology Problem to be solved by the invention Means for solving the problem (Fig. 1) Action Example (Figs. 2 to 5) EFFECTS OF THE INVENTION [Outline] Regarding a command exclusive control method, when processing an input / output command from a plurality of host devices, even if the input / output command terminates abnormally by a simple control by a microprogram, subsequent command processing is performed. In order to enable independent control for each command so that it will not be adversely affected, the command control table that stores the management information necessary for command execution control is set to the number of host devices (N). Than 1
When the command is issued from the host device, the base address of each region is set in correspondence with the command receiving region and the host device region, respectively. , The received command is stored by using the base address of the command control table prepared in the command receiving area, and the base address set in correspondence with the host device and the command reception when the command is executed After exchanging with the base address set for the purpose, the command is executed.

[Industrial applications]

The present invention relates to a command exclusion control method, and more specifically, to an input / output command processing for executing data reading or writing to an input / output device such as a magnetic disk device, an optical disk device, or a magnetic tape device. In particular, the simple control by the firmware enables independent control for each command issued from multiple host devices, regardless of whether the previous command completed normally or not. The present invention relates to a command exclusive control method that enables the.

[Conventional technology]

2. Description of the Related Art In recent years, as the performance and capacity of computer systems have increased, peripheral auxiliary storage devices such as magnetic disk devices have been required to have expanded storage capacity, reduced size, and improved performance.

Furthermore, in the case of a system in which multiple host devices share a magnetic disk device, etc., the control device of each input / output device efficiently and accurately processes the input / output commands issued from each host device one after another. There is a need to.

When receiving an input / output command from the host device and executing the command, the input / output device needs mechanical operation, and in order to improve the bus usage efficiency while not performing data transfer for a certain time, It has a function of temporarily releasing the connection state of the bus with the host device. Such an input / output device (control device) receives an input / output command from one host device, and when an input / output command is issued from another host device while executing the command, the command Because the command of is being processed, it cannot be executed immediately.

In this case, when the command issued later is received (b), the host device that issued the command
Immediately report that execution of the command cannot be started (for example, report BUSY status), do not execute the command, or (b), temporarily stack the command received later, and The execution of the command was completed, and the execution result was reported before the execution was controlled.

[Problems to be Solved by the Invention]

The conventional device as described above has the following drawbacks. That is, in the case of the above (a), it is not possible to specify how long the input / output operation currently being executed with respect to another host device continues.

Therefore, the command may have to be issued many times, and in such a case, useless processing is performed. It may also hinder the use of the bus of other host devices.

In the case of (b) above, while the command received later is being stacked, if the processing of the command received earlier ends abnormally, it may be difficult to control the command received later to execute normally. is there.

For example, whether the control device is currently executing an input / output command, or a plurality of tables for storing the input / output command and flags and variables for controlling the execution of the command are stored in the RAM in the control device. To prepare for
It also has a flag to indicate which table is in use. Therefore, there are many cases in which command processing ends abnormally, and it is necessary to operate the flag in all cases.

Also, it is difficult to confirm whether or not the processing at the time of abnormal termination of a large number of input / output commands has been correctly performed in all cases.

After all, in the case of a system in which multiple host devices share input / output devices, in order to execute the input / output commands issued from each host device, the control device of each input / output device can perform complicated processing by a microprogram. Often controlled.

Therefore, if there is a bug (error) in the microprogram and the flag operation is wrong even in one of the numerous abnormal terminations of the I / O commands described above, the I / O device will always be in operation, and commands etc. will be stored. The table to be used is always in use.

For this reason, not only the host device that issued the abnormally terminated command, but also other host devices may interfere with the input / output operation for this input / output device.

The present invention eliminates such a conventional drawback, and when processing an input / output command from a plurality of host devices, even if the input / output command terminates abnormally by simple control by a microprogram, The purpose is to enable independent control for each command so as not to adversely affect the command processing.

[Means for solving the problem]

FIG. 1 is a principle view of the present invention, and the principle of the present invention will be described below based on this figure.

According to the present invention, one or a plurality of host devices and one or a plurality of input / output devices are connected to a common bus, and input / output commands (commands) issued from the host devices to the input / output devices. The present invention is applied to a system in which a host computer is controlled by a microprocessor and a microprogram, and is particularly effective when a plurality of host devices share an input / output device.

FIG. 1A is an explanatory diagram of a RAM area in a control device provided in an input / output device in the above system.

In the figure, 22-2 is a command control table (RA
22-2-1 and 22-2-, respectively.
, 22-2-3, ..., 22-2- (N + 1) areas (in this area, there are +1 areas of the number of host devices that access the input / output devices).

This command control table 22-2 includes commands and
It stores variables necessary for command execution control, control flags, the name of the host device that issued the command, the end status of the command (information about normal end or abnormal end), and the like.

22-1 is a base address (1) of each command control table used by the microprocessor to access the command control table 22-2,
(2), (3) ... (N + 1) is the base address storage table area of the command control table.

This area is one command receiving area 2-1-1.
And one host device area 2-1-2, 2-1-3, ... 2-1 (N + 1) corresponding to each host device.

FIG. 1B is a diagram showing a control flow chart of the present invention, which will be described below with reference to FIG. 1A based on this diagram.

First, when the power is turned on, the command control tables {22-2-1 to 22-2 to 1 are stored in the base address storage table 22-1 in the command reception and host device areas as initial values.
22-2- (N + 1)} base address (1),
(2), (3) ... (N + 1) are set one by one (a).

Next, when the control device receives the input / output command (input / output command) issued by the host device (b), the base address, which is the data indicating the area of the command control table to be used when the command is received, is changed to the base address. The command is fetched from the command receiving area 22-1-1 in the storage table 22-1, and the received command or the like is stored in the command control table indicated by this base address (c).

Next, in the base address storage table 22-1, the base address set in the command receiving area 22-1-1 and the host device area prepared corresponding to the host device that issued the command {22-1-
2-22-1- (N + 1)} is exchanged with the base address set in any area (d).

Then, the data (base address) indicating the area in which the command to be executed is stored is passed to the command execution, and the command execution unit executes the command (e). In this case, the command execution unit analyzes the command issued from the host device and executes the input / output operation according to the instruction of the command. For example, in the case of a magnetic disk device, if it is a read command, the magnetic head is sought (moved) to the target track (target track) specified by the read command, and after reading the target sector,
It controls the transfer of read data to the host device.

The above control is repeated (ro-ho) to process the command from each host device.

[Action]

Since the present invention is configured as described above, it has the following effects.

The number of tables for controlling command execution (command control table) is set to be one more than the number of host devices, and each table 22-2-1 to 22-2-is used when accessing that table. A table for storing (N + 1) base addresses (base address storage table) is held for command reception and corresponding to each host device.

That is, each command control table 22-2-1 to 22-
The base addresses (1) to (N + 1) of 2- (N + 1) are always set in any of the tables 22-2-1 to 22-2- (N + 1).

Therefore, the base address of the command control table 22-2 in which the commands issued by the host device are stored is set in the corresponding base address storage table 22-1.

Therefore, the command control table 22-2 pointed to by the base address storage table 22-1 stores the command or the like currently being executed by the corresponding host device, or the command having been executed.

The command control table indicated by the table prepared for command reception stores the commands and the like that have been executed.

In other words, since the command control table that is not in use is always prepared, when a command is received from the host device, the command reception table is not searched without searching which command control table is in use. It is possible to take out the address information of the command control table from the base address storage table 22-1-1 for use and immediately store the received command in the command control table indicated by this command information.

By the way, in the conventional device, each command control table is provided with a flag indicating whether it is in use, and when a command is received from the host device, which command control table is not used is searched. Thus, the received command is stored in the unused command control table.

For this reason, when abnormally ending a command that has occurred during execution of input / output processing instructed by a command (error during control of mechanical operation, error during data transfer with host device, etc.), It was necessary to reset the flag indicating that the command control table used was in use.

However, due to an error in the firmware, if this flag is not reset even in one of the many abnormal processes, the command control table will always be in use and will not be used again. There was a problem that I could not do it. Further, if such an erroneous operation of the flag occurs several times, even if a new command is received, there is no command control table for storing the command.

On the other hand, in the present invention, it is not necessary to provide a flag or the like indicating the usage state of the command control table used in the conventional apparatus, and the command control table is used regardless of whether the command is normally ended or abnormally ended. It is not necessary to operate the flag indicating the state.

When the host device issues one command, it does not issue a new command until the command is completed. Therefore, the input / output device must have a function of receiving only one command from one host device. Further, when the input / output device is executing a command issued from a certain host device and a command is issued from another host device, a function of receiving the command is also required.

The present invention does not cause the problem that the command control table is always in use even if the commands are satisfied and the command ends abnormally. There is no adverse effect.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a system configuration diagram used in one embodiment of the present invention. In the figure, 1-1, 1-2, 1-3 ... 1-N
Is a host device (upper computer system including a central processing unit, etc., 2A, 2B are magnetic disk control devices, 3A, 3B
Is a magnetic disk device, 4 is a host device 1-1, 1-2,
1-3 ... 1-N and the magnetic disk control devices 2A and 2B are connected to a higher-level interface (common bus), 5A and 5B, the magnetic disk control device 2A or 2B and the magnetic disk device 3A.
Or it shows the lower interface to connect with 3B.

In this system, the host devices 1-1 to 1-N issue an input / output command to the magnetic disk control device 2A or 2B via the upper interface 4, and the magnetic disk control device 2A or 2B is connected to the lower interface 5A or 5B. The magnetic disk device 3A or 3B is controlled via the, and the operation specified by the command is executed.

FIG. 3 is a block diagram of a magnetic disk control device, and illustrates one device used in the system shown in FIG.

In the figure, 2 is a magnetic disk control device, 3 is a magnetic disk device, 4 is an upper interface, and 5 is a lower interface.

Further, 20 is an MPU (microprocessor), 21 is a ROM (read only memory), 22 is a RAM, 23 is an upper interface control unit, 24 is a lower interface control unit, and 25 is a data buffer.

The MPU 20 controls operations such as command processing in the magnetic disk control device, and the ROM 21 stores micro programs.

The RAM 22 is a memory used by the MPU 20, and the upper interface control unit 23 performs command reception, execution result transmission, data transfer, interface protocol control, and the like.

The lower interface control unit 24 performs data transfer, interface protocol control, etc.
The numeral 25 is for efficiently executing data transfer between the magnetic disk device 3 and the host device.

FIG. 4 is a block diagram of the RAM shown in FIG.
The same reference numerals as those in FIG.

The RAM 22 has a command control table 22-2 and a command control table base address storage table 22-2.
-1 and -1 are provided.

The command control table 22-2 has one more N + than the number N of host devices that access the input / output device.
One area 22-2-1 to 22-2- (N + 1) is provided, and when the command issued from the host device is received, the area 22-2-1 to 22-2- (N + 1) is provided. ), The command, variables necessary for controlling the execution of the command, control flags, the name of the host device that issued the command, the end status of the command (normal end or abnormal end), etc. are stored.

The base address storage table 22-1 includes areas 22-2-1 to 22-2- (N) of the command control table 22-2.
There is an area corresponding to +1).

This area is one command receiving area 22-1-1.
And each host device area 22-1-2 to 22-1- (N +
1) and each area of the command control table 22-2
The base addresses of 22-2-1 to 22-2- (N + 1) are stored correspondingly.

FIG. 5 is a control flowchart of the above embodiment,
This will be described with reference to FIGS.

First, when the power is turned on, an initial value is set by the microprogram in the ROM 21 (h). This is a command receiving area 22-1-1 and host device areas 22-1-2 to 22-1 provided in the base address storage table 22-1 on the RAM 22.
This is performed by setting the base address of each of the areas 22-2-1 to 22-2- (N + 1) in the command control table 22-2 in correspondence with-(N + 1).

Next, if the received command has (i), the command control table indicated by the base address (1) is used by using the base address (1) set in the command reception area 22-1-1. Area 22-2
The command and the like are stored in -1 (nu).

Then, it is determined whether the received command requires a certain time (T time or more) until the command processing is completed (L).

As a result, when executing the command, if the input / output device (the magnetic disk devices 3A and 3B in the embodiment) requires a mechanical operation, such as when the command processing requires the time T or more, Cancel the bus connection state of
The base address (1) set in the command receiving area 22-1-1 and the host device 1-1 area 22-1-
The base address (2) set to 2 is exchanged (e).

That is, the address held in the command receiving area 22-1-1 and the address held in the host device 1-1 area 22-1-2 are read out, and then the command receiving area 22-1-1. 1 is set in the area 22-1-2 for the host device 1-1, and the address read from
The address read from the working area 22-1-2 is set in the command receiving area 22-1-1. By this operation,
A command control table used when receiving a new command is prepared.

When a command process requiring more than T time is being executed, another host device may issue a command in order to release the connection state of the bus with the host device. When a command that requires more than T time is received from another host device during command execution, that command cannot be executed immediately, so it is necessary to wait (stack) until the command processing being executed is completed. There is. Therefore, when a command that requires more than T time is received (L),
Judge whether the command is currently being executed (W).

After that, if the command can be executed immediately (wa), the command execution is started (f), but if the command is currently being executed and cannot be executed immediately, the command is stacked (yo). Nothing is done when the commands are stacked, but when the command being executed is finished, the command is searched for the stacked commands. If there is an unexecuted command for any of the host devices, execution of that command is started.

Further, in the above case, if the command processing time is less than T time, the command execution is immediately started regardless of whether the command from another host device is currently being executed. If the command received during execution of a command from another host device is a command that can be executed within T time, it is originally executed after interrupting the processing of the command currently being executed and executing a new command. Continue processing the command.

In the process of executing such a command, while the first command is being executed, another host device, for example, the host device 1
-2, when the command is issued, the base address set in the command reception required area 22-1-1 (2)
Area of the command control table pointed to by the base address (2) in the command reception area 22-1-1 using
The received command etc. is stored in 22-2-2.

When the received command requires a certain amount of time to complete the command processing (T time or more), the base address (2) set in the command receiving area 22-1-1 and the host device 1-2 are set. For exchanging the base address (3) set in the area 22-1-3 of the corresponding table for execution, execution or stacking of the command is started.

However, if the command is a command that can be processed for a short time, execution of the command is immediately started.

Similarly, the command execution is controlled by operating the base address (pointer) of the command control table.

The device of the above embodiment is an example applied to a magnetic disk device equipped with a SCSI interface. In this case,
The function when the same host device issues multiple commands is not defined. Therefore, the device of the above embodiment is
The same host device cannot support the function of issuing a plurality of commands (command queuing function).
That is, since the device of the above embodiment does not have a function of stacking a plurality of commands from the same host device, it can be applied to a system that does not use the command queuing function.

In the above embodiment, the example applied to the magnetic disk device has been described, but it is also applicable to various input / output devices such as an optical disk device and a magnetic tape device.

Further, when a plurality of host devices are provided, it is particularly effective, but it is also applicable to a system having one host device.

〔The invention's effect〕

As described above, the present invention has the following effects.

Even in a system where I / O devices are shared by multiple host devices, when an I / O command issued from each host device is executed, any abnormal termination of the I / O command can be performed by simple control by the microprogram. Even in this case, independent control can be performed for each command so as not to adversely affect the subsequent command processing.

[Brief description of drawings]

FIG. 1 is a principle diagram of a command exclusive control method according to the present invention, FIG. 2 is a configuration diagram of a system used in one embodiment of the present invention, and FIG. 3 is a block of the magnetic disk control device shown in FIG. FIG. 4 is a block diagram of the RAM shown in FIG. 3, and FIG. 5 is a control flow chart of one embodiment of the present invention. 22-2 ...... Command control table 22-1 ...... Command control table base address storage table

Claims (1)

(57) [Claims] 1. A command exclusion control method for controlling a command for an input / output device, which is connected to a common bus and is issued from one or a plurality of host devices, by a control means of the input / output device. The command control table (22-2) for storing the received command and the command control information necessary for controlling the execution of the command is added to the area {22-2 which is one more than the number (N) of the host devices. -1 to 22-2-
(N + 1)}, and the control means sets the command control table (22-
2) the base address of each of the areas {22-2-1 to 22-2- (N + 1)} used when accessing to the command receiving area (22-1-1) and each host device For each of the command areas {22-1-2 to 22-1- (N + 1)}, and when a command is issued from the host device, the command receiving area (22-1- Using the base address of the command control table prepared in 1), the received command is stored in a predetermined area of the corresponding command control table, and the host that issued the command when executing the command The base address of the command control table set corresponding to the device and the base of the command control table set for receiving the command used when receiving this command After exchanging the dress, the command exclusive control method characterized by executing the command.