JP2000194654A - Unit and method for scsi bus priority control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow SCSI devices to equally obtain the right to use a bus by omitting the operation of an arbitration phase and starting a selection phase at a request from a bus emergency request means. SOLUTION: A bus monitor part 30 once detects the arbitration phase informs an arbitration phase timer part 31 of that. The arbitration phase timer part 31 measures the arbitration phase time and informs a bus emergency request part 32 of the elapse of a bus-free delay time. The bus emergency request part 32 once informed of an emergency access instruction and the bus-free delay time elapse instructs a SCSI bus control part 23 to start the selection phase. The SCSI bus control part 23 omits the arbitration phase and sends its ID number, the ID number of a target SCSI device, and number and a SEL signal to the SCSI bus to start the selection phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a control system for a SCSI bus, and more particularly to an improvement in a control system for acquiring a bus use right.

[0002]

2. Description of the Related Art Generally, a SCSI bus has a bus free phase, an arbitration phase, a selection phase, a reselection phase, a command phase,
It operates according to transition of eight types of bus phases including a data phase, a status phase, and a message phase. Among the bus phases, an arbitration phase is a phase for the SCSI device to acquire the right to use the bus.

In the arbitration phase, a SCSI device that wants to acquire a bus use right outputs a data bit corresponding to its own preset ID number on a data bus, and among the SCSI devices that output data, the ID number is changed. The largest SCSI device can get the bus usage right.

As an example of an arbitration operation in a SCSI bus, FIG. 6 shows an operation timing when a request for a bus use right is issued to the host devices 4 to 7 in the SCSI bus system shown in FIG.

In FIG. 6, a period 301 is a bus free phase, in which all SCSI devices do not use the bus. The period 302 is an arbitration phase in which the SCSI device acquires the right to use the bus.

[0006] The host devices 4 to 7 participating in the arbitration of the right to use the bus use the minimum Bus Fr after detecting the bus free.
After waiting for the ee Delay time, a BSY signal and data corresponding to its own ID number are output to the data bus to request a bus use right. In this example, the host devices 5 to 7 participate in the arbitration almost at the same time, and the host device 4 participates in the arbitration with a slight delay.

Each of the host devices 4 to 7 outputs the BSY signal and the data corresponding to its own ID number to the data bus and compares the values on the data bus after the elapse of the Arbitration Delay time or more, and requests the bus use right. Is determined. In this example, as a result of comparing the values on the data bus, the host device 7, which has transmitted the ID number having the highest priority, outputs the SEL signal and acquires the right to use the bus.

The host devices 5 and 6 detect that a SCSI device having a higher priority than themselves requests the right to use the bus, and stops outputting signals to the bus within the Bus Clear Delay time. Also, the host device 4 detects that the SEL signal is being output on the bus while the arbitration is in progress (before the Arbitration Delay time has elapsed), and
Stop signal output to the bus within the Clear Delay time. A period 303 is a selection phase in which the SCSI device that has acquired the bus usage right transfers data to the SCSI device.
This is a phase for selecting an I device.

After outputting the SEL signal, the host device 7 waits for at least Bus Clear Delay + Bus Settle Delay time, and the ID number of the host device 7 and the I of the data transfer partner.
The D number is output from the data bus.

In other words, the bus arbitration operation in the conventional SCSI bus employs a fixed priority control system that determines the bus use right of each SCSI device by associating the ID number with the bus acquisition priority on a one-to-one basis. For this reason, when the bus usage rate is high, the bus usage rights are not averaged. In particular, when the bus usage frequency of the SCSI device with the large ID number is high, the SCSI device with the small ID number takes time to acquire the bus usage right. And processing that requires immediacy is difficult.

In order to respond to this request, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-335203, by circulating the criteria for judging the magnitude of the ID number for each arbitration phase, a plurality of SCSI devices can be fairly distributed. There is a method of giving a bus use right. As another example, there is a method in which a controller counts the number of bus acquisition failures of each SCSI device, and preferentially gives a bus use right to a SCSI device having a large number of bus acquisition failures. Such a method is disclosed, for example, in Japanese Patent Application Laid-Open No. 64-12325.

[0012]

However, by circulating the criteria for judging the magnitude of the ID number, a plurality of SCSI
In the method of imparting the right to use the bus fairly to the device, the priority is rotated in a fixed direction for each arbitration.
If the priority is the lowest when the bus use right request of the CSI device is generated, the order waits until the high priority starts again. (Since arbitration needs to be performed seven times until the priority becomes the highest, the queue waits up to seven times.)

Further, a method in which the controller counts the number of bus acquisition failures of each SCSI device and preferentially assigns the bus use right to the SCSI device having a large number of bus acquisition failures is to judge the bus priority only by the number of bus acquisition failures Therefore, if the SCSI device with a large ID number has a high bus usage frequency, the bus usage right cannot be obtained unless the bus acquisition for the set number of times fails.

The present invention has been made in consideration of the above points, and a main object of the present invention is to provide a plurality of SCSI devices with an SCS.
An object of the present invention is to provide a SCSI bus control system capable of averaging acquisition of a bus use right of each SCSI device in a SCSI bus system connected to the I bus.

[0015]

In order to achieve the above object, a SCSI bus priority control device according to a first aspect of the present invention includes a SCSI bus priority control device which is connected to another SCSI device connected to the SCSI bus. An apparatus for performing usage right priority control, comprising: bus monitoring means for monitoring the SCSI bus; arbitration phase timer means for measuring an arbitration phase time in response to detection of an arbitration phase by the bus monitoring means; Bus emergency request means for instructing the start of the selection phase during measurement of the arbitration phase time by the arbitration phase timer means, and arbitration phase operation is omitted by a request from the bus emergency request means. do it S to start a record action phase
And CSI bus control means.

Further, the SCS according to the second aspect of the present invention
The I-bus priority control device is a device that performs priority control of the right to use the SCSI bus with another SCSI device connected to the SCSI bus, the bus monitoring means monitoring the SCSI bus, and the bus monitoring device. Arbitration phase timer means for detecting that a predetermined time has not elapsed since the occurrence of the arbitration phase by the means; and the bus monitoring means when the arbitration phase timer means detects that the predetermined time has not elapsed. When a signal indicating the presence of the SCSI device that has started the selection phase is detected on the SCSI bus, a bus emergency request means for instructing the stop of the operation of the arbitration phase, and arbitration by a request from the bus emergency request means. And characterized by including a SCSI bus control unit to stop the operation of the Phase.

In the SCSI bus priority control apparatus according to the present invention, even if the SCSI device has a low priority, if a bus urgency request with high urgency is generated within itself, the
Bus monitoring means for monitoring a bus control signal and detecting an arbitration phase; and a self-ID number and a target SC during the arbitration phase.
SCSI bus control means for determining the selection phase within the Bus Free Delay time by transmitting the ID number of the SI device and the SEL signal to the SCSI bus, thereby using the own bus regardless of the priority of the SCSI device. You can get the right.

A normal SCSI device detects an arbitration phase according to the specification of the SCSI bus, and
It is necessary to wait for a predetermined time, that is, the Bus Free Delay time, before requesting the right to use the bus.

In the present invention, since the selection phase is determined during the Bus Free Delay time, other SCSI devices cannot execute arbitration of the bus usage right and cannot acquire the bus usage right. Therefore, when an urgent bus use right request is issued to the SCSI device, the bus use right can be acquired as soon as the use of the current SCSI bus ends, regardless of the ID number (priority of acquiring the bus use right).

Further, a SCSI according to a third aspect of the present invention
The bus priority control method uses another S bus connected to the SCSI bus.
A SCSI bus priority control method for performing priority control of the right to use the SCSI bus with a CSI device, the method comprising monitoring the SCSI bus, detecting an arbitration phase, measuring an arbitration phase time,
When a request for the right to use the bus occurs, instructing the start of the selection phase during the measurement of the arbitration phase time, and omitting the operation of the arbitration phase and starting the selection phase according to the request. I do.

A SCSI according to a fourth aspect of the present invention
The bus priority control method uses another S bus connected to the SCSI bus.
In the SCSI bus priority control method for performing priority control of the right to use the SCSI bus with a CSI device, the SCSI bus is monitored to detect that a predetermined time has not elapsed after the occurrence of an arbitration phase, When it is detected that the above has not elapsed, when the SCSI device that has started the selection phase is detected, an instruction to stop the operation of the arbitration phase is issued, and the operation of the arbitration phase is stopped upon request. And

[0022]

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

FIG. 1 shows an SC according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of an SI bus system. FIG.
Are SCSI devices, magnetic disk devices (hereinafter referred to as HDDs) 0 to 3;
Host devices 4 to 7 that perform data input / output control with the HDDs 0 to 3 are interconnected via a SCSI bus 8. Here, IDs are assigned to HDDs 0 to 3 respectively.
Numbers 0 to 3 are set, and ID numbers 4 to 7 are set in the host devices 4 to 7, respectively.

FIG. 2 is a block diagram showing a functional configuration of the host devices 4 to 7 shown in FIG. As shown in FIG. 2, the host device includes a CPU 20 and an HDD controller 21. The HDD controller 21 has C
CPU interface unit 22 that communicates with PU 20
And a SCSI bus control unit 23 for controlling the SCSI bus
And an S that accommodates an electrical interface of the SCSI bus
A CSI interface unit 24 and a bus monitoring unit 30 for monitoring a state based on a SCSI bus control signal
And an arbitration phase timer unit 31 for measuring the arbitration phase elapsed time when the arbitration phase detection is notified from the bus monitoring unit 30
Receives an emergency bus request command from the CPU 20,
The function of the bus emergency request unit 32 for instructing the SI bus control unit 23 to start the selection phase is included.

Next, the operation of the SCSI bus system of this embodiment for acquiring the right to use the bus will be described. Here, a case will be described as an example where the host apparatus 4 having a low priority of acquiring the bus use right urgently requests the acquisition of the bus use right.

The CPU 20 of the host device 4 urgently
When data transfer with D is required, the target HDD is designated to the HDD controller 25 and an emergency access command is issued.

The CPU interface unit 22 has a SCSI
The target HDD is notified to the bus control unit 23, and the emergency access command is notified to the bus emergency request unit 32.

On the other hand, when the bus monitoring unit 30 constantly monitors the SCSI bus and detects an arbitration phase, it notifies the arbitration phase timer unit 31 of the detection of the arbitration phase. The arbitration phase timer unit 31 measures the arbitration phase time and notifies the bus emergency request unit 32 that the Bus Free Delay time has elapsed.

The bus emergency request unit 32 is provided with an emergency access command from the CPU interface unit 22 and a Bus Free Delay from the arbitration phase timer unit 31.
Upon receiving the notification of the elapse of time, it instructs the SCSI bus control unit 23 to start the selection phase.

The SCSI bus control unit 23 omits the arbitration phase in response to a request from the bus urgent request unit 32, and sets its own ID number and the target SC
The ID number of the SI device and the SEL signal are transmitted to the SCSI bus 8, and the selection phase is started.

On the other hand, the host devices 7 to 5
Arbitration operation starts after elapse of ay time,
The bus monitor 30 detects that the SEL signal is output on the SCSI bus 8. The bus monitoring unit 30 of each of the host devices 7 to 5 notifies the bus emergency request unit 32 of the detection of the SEL signal. The arbitration phase timer unit 31 measures the elapsed time of the arbitration phase, and determines whether the bus arbitration phase has elapsed.
It notifies the bus emergency request unit 32 that the delay time has not elapsed.

The bus emergency request unit 32 determines that a bus emergency request has occurred on the SCSI bus 8 and
Before the tration delay time has elapsed, the SCSI bus control unit 23 is instructed to stop the arbitration operation.

As a result, the host devices 5 to 7 do not execute the operation in the arbitration phase, and
The host device 4 that urgently needs the right to use the bus can acquire the right to use the bus.

Next, the operation of acquiring the right to use the bus on the SCSI bus 8 will be described with reference to the timing chart of FIG.

In the SCSI bus system shown in FIG. 1, a case where an urgent data transfer request is issued to the HDD 0 inside the host device 4 will be described below.

During the period 300, the host device 7 is using the bus. At this time, a bus emergency request has been generated inside the host device 4. The period 301 is a bus free phase, in which all SCSI devices
The bus 8 is not used.

The period 302 is an arbitration phase in which the SCSI device acquires the right to use the bus. The host devices 5 to 7 participating in the arbitration of the bus usage right wait for the minimum Bus Free Delay time after detecting the bus free, and request the bus usage right. Output to bus bit. After this, Arbitratio
Arbitration participant waits until n Delay time elapses.

On the other hand, since the bus urgent request is generated internally, the host device 4 waits for the BusFree Delay time and then waits for the own ID number and the I / O of the target HDD0.
Outputting data corresponding to the D number to a data bus bit,
Start the selection phase.

The period 303 is a selection phase when a bus emergency request occurs, and is a phase in which the SCSI device (initiator) that has acquired the bus use right selects a SCSI device to operate as a target. The host device 4 has its own ID number and target H
After outputting the data bus bit corresponding to DD0,
After waiting for Delay × 2 hours, the SEL signal is output.

Host devices 5-7 requesting the right to use the bus
Detects that the SEL signal is output on the data bus before the elapse of the Arbitration Delay time, determines that there is a SCSI device requesting the right to use the emergency bus, and stops arbitration. At this point, the acquisition of the bus use right of the host device 4 is determined.

As described above, even if the host device 4 has a low priority of acquiring the bus use right, when the bus use right request with high urgency is generated, the bus monitoring unit 30 sets the SC.
When monitoring the SI bus 8 and detecting a bus free phase, the SCSI bus control unit 23 skips the arbitration phase and starts the selection phase before the other host devices 5 to 7 execute the operation of the arbitration phase. You can get your own right to use the bus. Therefore, the SCSI device having the higher priority does not always acquire the bus use right.
The acquisition of the bus use right of the CSI device can be averaged.

Next, another embodiment of the present invention will be described. The above description based on the configuration shown in FIG. 1 is directed to a case where one host device 4 issues an urgent request for the right to use the bus, but here, an urgent request for the right to use the bus is issued from a plurality of host devices. The following shows a configuration that can cope with the case where there is.

FIG. 4 shows the configuration of a host device according to another embodiment. The basic configuration is the same as FIG. 1, but
An ID register unit 42 for controlling the timing of acquiring the SCSI bus is provided. In FIG. 4,
Parts that perform the same operations as in FIG. 1 are denoted by the same reference numerals as in FIG.

As shown in FIG. 4, the ID register 42
Are connected to an arbitration phase timer unit 41. The ID register 42 stores its own ID number.

Arbitration phase timer section 41
Notifies the bus emergency request section 32 of the elapse of the Bus Free Delay time when a bus emergency request occurs. At this time, the ID number is referenced from the ID register section 42,
Change the notification timing according to the number.

FIG. 5 shows the operation timing of the arbitration phase timer 41 using the variable notification timing to notify the elapse of the Bus Free Delay time.

In the example shown in FIG. 5, the ID register unit 42 of the host device having the smaller ID number is configured to execute the notification of the elapse of the Bus Free Delay time to the bus urgent request unit 32 earlier. As a result, the timing for starting the selection phase of each host device differs according to the difference in the ID number.

For this reason, for example, even when a bus urgent request is generated from two host devices at the same time, the right to use the bus is acquired by the order based on the timing difference determined according to the ID number, that is, the fixed priority control. Becomes possible.

In the above description of the other embodiments, the fixed priority control is performed by changing the timing of starting the selection phase based on the ID number even when bus emergency requests are simultaneously generated from a plurality of host devices. However, in the ID register unit 42, each host device (SC
Non-fixed priority control is provided by providing a calculation function for generating a unique numerical value for each SI device) and notifying the bus emergency request unit 32 at a timing corresponding to the numerical value obtained by this calculation function. , A bus use right acquisition function can be realized.

It should be noted that the present invention is not limited to the above embodiments, and it is clear that the embodiments can be appropriately modified within the scope of the technical idea of the present invention.

[0051]

As described above, according to the present invention,
In a bus to which a plurality of SCSI devices are connected, a low-priority SCSI device monitors a control signal of the SCSI bus when a highly urgent bus use right request is generated within itself, and detects a bus free phase, and By transmitting the ID number, the ID number of the target SCSI device, and the SEL signal to the SCSI bus, it acquires its own right to use the bus and determines the selection phase.
A priority bus use right acquisition function that realizes a bus use right acquisition of a CSI device is provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a SCSI bus system.

FIG. 2 is a block diagram showing a functional configuration of the host device shown in FIG. 1 in the embodiment of the present invention.

FIG. 3 is a timing chart showing an operation of acquiring a bus use right on a SCSI bus according to the embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a host device according to another embodiment of the present invention.

FIG. 5 is a timing chart showing an operation timing of a Bus Free Delay time elapse notification of an arbitration phase timer unit according to another embodiment of the present invention.

FIG. 6 is a SCSI bus timing chart showing a normal SCSI bus arbitration operation.

[Explanation of symbols]

 0-3 Hard disk device (HDD) 4-7 Host device 8 SCSI bus 20 CPU 21 HDD controller 22 CPU interface unit 23 SCSI bus control unit 24 SCSI interface unit 30 Bus monitoring unit 31 Arbitration phase timer unit 32 Bus emergency request unit 40 Arbitration Phase timer section 42 ID register section

Claims (5)

[Claims] 1. A SCSI bus priority control device for performing priority control of the right to use the SCSI bus with another SCSI device connected to the SCSI bus, comprising: bus monitoring means for monitoring the SCSI bus; Arbitration phase timer means for measuring an arbitration phase time in response to the detection of the arbitration phase by the means; Bus emergency request means for instructing start, and SCSI bus control means for omitting the operation of the arbitration phase and starting the selection phase in response to a request from the bus emergency request means. SCSI bus priority control device. 2. A SCSI bus priority control device for performing priority control of the right to use the SCSI bus with another SCSI device connected to the SCSI bus, comprising: bus monitoring means for monitoring the SCSI bus; Arbitration phase timer means for detecting that a predetermined time has not elapsed since the occurrence of the arbitration phase by the means; and when the arbitration phase timer means has detected that the predetermined time has not elapsed, the bus monitoring means When a signal indicating the presence of the SCSI device that has started the selection phase is detected on the SCSI bus, the bus emergency request means for instructing to stop the operation of the arbitration phase; A SCSI bus control means for stopping the operation of the translation phase. 3. The system according to claim 1, wherein the timing at which the detection result of the arbitration phase timer is transmitted to the bus emergency requesting unit is determined based on information unique to a SCSI device. SCSI bus priority controller. 4. A SCSI bus priority control method for performing priority control of the right to use the SCSI bus with another SCSI device connected to the SCSI bus, wherein the SCSI bus is monitored to detect an arbitration phase. The arbitration phase time is measured, and when a request for the right to use the bus occurs, the start of the selection phase is instructed during the measurement of the arbitration phase time, and the operation of the arbitration phase is skipped according to the request. A SCSI bus priority control method. 5. A SCSI bus priority control method for performing priority control of the right to use the SCSI bus with another SCSI device connected to the SCSI bus, wherein the SCSI bus is monitored and a predetermined time is set when an arbitration phase occurs. It is detected that the time has not elapsed, and when it is detected that the predetermined time has not elapsed, when the SCSI device that has started the selection phase is detected, the operation of the arbitration phase is instructed to be stopped, An SCSI bus priority control method, wherein the operation in the arbitration phase is stopped by a request.