JP2502850B2 - Communication method for SCSI system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of SCSI (Small Compu) that are initiators or targets.
ter System Interface) device
The present invention relates to a system connected to a CSI bus, and more particularly, to a communication method of a SCSI system that improves processing operation efficiency when a command is sent from an initiator to a target to perform a predetermined process.

[0002]

2. Description of the Related Art In a data communication system in which devices supporting SCSI-1 level standards (SCSI devices) are connected by a SCSI bus, a command is sent from one SCSI device (initiator) to another SCSI device (target). It is common to send and receive data. FIG. 4 shows an example of the configuration of a SCSI communication system in the case where the initiator is a host computer and the target is a communication device in such a SCSI system. In the figure, reference numeral 1 is a SCSI-1 level host computer corresponding to an initiator, 2 is a communication device connected to a communication line 3 and corresponds to a target, 4
Is a SCSI bus connected between the host computer 1 and the communication device 2. Such SCSI
In the system, when the communication device 2 makes a data reception request (Ring) to an external communication terminal (hereinafter, referred to as an external terminal) through the communication line 3 under the instruction of the host computer 1, and receives data. A conventional example of the receiving procedure is shown in FIGS.

FIG. 5 shows a reception procedure in which an asynchronous input from an external terminal is notified from the communication device 2 to the host computer 1 by a polling operation. In this receiving procedure, first, the SCSI bus is selected from the bus-free state toward the communication device 2 from the host computer 1, an identify message is transmitted, and subsequently a request sense command is transmitted. In response to this,
Communication device 2 has sense data and good
A status signal and a command complete message are sent to the host computer 1 to notify that polling reception will be performed. The host computer 1 receives the asynchronous notification by these signals. After that, a bus-free connection is established between both devices 1 and 2. While the bus is free, the communication device 2 makes a ring call to the external terminal and makes a data reception request by a polling operation.

After that, the host computer 1 makes a selection toward the communication device 2 and sends an identify message, followed by a get message command. In response to this, the communication device 2 returns the received data, and subsequently the good status and command
A complete message is sent to the host computer 1 to complete the data reception, after which the SCSI bus between both devices 1 and 2 becomes bus-free again.

FIG. 6 shows a receiving procedure in which an asynchronous input from an external terminal is notified from the communication device 2 to the host computer 1 by a reselection operation for a get message command. In this receiving procedure, first, the SCSI bus performs selection from the bus-free state toward the communication device 2 from the host computer 1 to perform identification / verification.
A message is sent, followed by a get message command. In response to this, the communication device 2 returns a disconnect message. After that, the SCSI bus becomes bus-free.

While the bus is free, the communication device 2 makes a ring request to an external terminal to receive data. When data is received from the external terminal, the communication device 2 performs reselection from the bus-free state toward the host computer 1. By this operation, the host computer 1 receives the asynchronous notification. Following this reselection, an identify message and received data are sent out, and subsequently, a good status signal and a command complete message are sent out to the host computer 1. After that, the SCSI bus between both devices 1 and 2 becomes bus-free again.

[0007]

However, in such a conventional communication method for a SCSI system, polling reduces the efficiency of use of the SCSI bus 4 and CPU time between the host computer 1 and the communication device 2. There is a problem in that the processing power of the host computer 1 and the communication device 2 is reduced due to the loss of data. Further, when the get message command is issued in the past, allocating the memory of the host computer for the SCSI communication means that the memory of the host computer 1 is occupied before the asynchronous notification occurs. 1 causes a decrease in CPU processing efficiency. Further, it may take time for the host computer 1 to allocate the memory of the host computer 1 at the time of the reselection in order to receive the data immediately after receiving the asynchronous notification by the get message command. The communication device 2 arbitrarily receives data from the communication line 3 causes a communication error (timeout).

The present invention has been made in view of the above problems, and an object thereof is to provide a communication method for improving the processing operation efficiency when transmitting / receiving data in a SCSI system.

[0009]

In order to achieve the above object, the present invention provides a system in which a SCSI bus is connected with a plurality of SCSI devices as an initiator and a target.
The gist is that when a response is returned from the target in response to a command from the initiator, a message sending operation for asynchronous notification is added to perform asynchronous notification.

As another method, when a command is sent from the initiator to the target, a command sending operation for asynchronous notification is added to separate asynchronous notification and data reception for each command.

As another method, an asynchronous notification is provided by providing an operation of sending a message for asynchronous notification from the target to the initiator, regardless of reception of a command sent from the initiator to the target. did.

[0012]

According to the above-described communication method of the present invention, the target to which a command is sent from the initiator on the SCSI bus sends a message for asynchronous notification to the SCSI bus when returning a response to this command, and the initiator Receiving a message and recognizing an asynchronous signal. Conversely, when sending a command from the initiator to the target, the initiator sends a command for asynchronous notification to the SCSI bus, and the target receives this command and adds a message for asynchronous notification to the response signal. Send on the SCSI bus.
Further, the target sends a message for asynchronous notification onto the SCSI bus regardless of the operation of the initiator sending a command to the target, and the initiator receives the message and recognizes the asynchronous signal. By performing asynchronous notification from the target to the initiator by any of these operations, this asynchronous notification is performed simply and in a short time, and the SCSI bus usage efficiency
And the operating efficiency of the host computer is improved.

[0013]

1 to 3 are time charts showing three kinds of embodiments of a communication method of a SCSI system according to the present invention. Also in these embodiments, the same hardware configuration as shown in FIG. 4 is used as the SCSI system. Further, in the present invention, as a method of notifying the initiator of the asynchronous input from the external terminal, a method of performing a reselection operation for the get message command is adopted.

FIG. 1 shows a first embodiment. In the receiving procedure in this embodiment, first, the SCSI bus is in a bus-free state, the selection command and the identify message are sent from the host computer 1 (initiator) to the communication device 2 (target), and then the get command is obtained. -A message command is sent. In response to this, the communication device 2 returns a disconnect message. After that, the SCSI bus between both devices 1 and 2 becomes bus-free.

During the bus-free period, the communication device 2 makes a ring call to the external terminal and makes a data reception request. Then, the communication device 2 performs reselection toward the host computer 1 and sends an identify message and a ring message which is a message for asynchronous notification. The ring message signal causes the host computer 1 to receive the asynchronous notification. After receiving these signals, the host computer 1 sends a wait message, which is a standby request, to the communication device 2, and the communication device 2 returns a disconnect message to the host computer 1. After that, SCS between both devices 1 and 2
The I-bus will be bus-free again.

Until data is received from the external terminal, the communication device 2 performs reselection toward the host computer 1 again at a fixed time interval, and then performs an identify message and a ring message. On the other hand, a wait message is sent from the host computer 1 to the communication device 2 and a disconnect message is sent back from the communication device 2 to the host computer 1. Then S between both devices 1, 2
The CSI bus will be bus-free again.

When data is received from the external terminal, the reselection command is sent from the communication device 2 to the host computer 1, followed by sending an identify message and received data, followed by a good message.・ Status signal and command complete message are sent to host computer 1
Sent to. After that, the bus between the two devices 1 and 2 becomes free again. With the above, the data receiving operation is completed.

FIG. 2 shows a second embodiment. In the receiving procedure in this embodiment, first, the selection command and the identify message are sent from the host computer 1 to the communication device 2 from the bus-free state, and then the ring answer command which is a command for asynchronous notification. Is sent. In response to this, the communication device 2 returns a disconnect message. Then both devices 1,
Bus free between 2

During this bus-free period, the communication device 2 makes a ring call to the external terminal and makes a data reception request. Then, as a response to the ring answer command, the communication device 2 sends a reselection command, an identify message, a good status signal, and a command complete message to the host computer 1. As a result, the host computer 1 receives the asynchronous notification.

Next, the selection command and the identify message are sent from the host computer 1 to the communication device 2, and subsequently the get message command is sent. In response to this, the communication device 2 disconnects
The message is returned. After that, a bus-free connection is established between both devices 1 and 2.

When data is received from the external terminal, the communication device 2 sends a reselection command to the host computer 1, then sends an identify message and received data, and then continues. A good status signal and a command complete message are sent to the host computer 1. Then both devices 1, 2
In the meantime, the bus will be free again. With the above, the data receiving operation is completed.

FIG. 3 shows a third embodiment. In the receiving procedure in this embodiment, first, while the SCSI bus is bus-free, the communication device 2 makes a ring call to an external terminal to make a data reception request. Thereafter, the communication device 2 performs reselection toward the host computer 1 regardless of whether or not a command is sent from the host computer 1 to the communication device 2, and an identify message and a ring answer message. And a command complete message is sent. As a result, the host computer 1 receives the asynchronous notification.

Next, the host computer 1 makes a selection toward the communication device 2 and sends an identify message, followed by a get message command. In response to this, the communication device 2 disconnects
The message is returned. After that, the SCSI bus between both devices 1 and 2 becomes bus-free.

When data is received from an external terminal, the communication device 2 performs reselection toward the bus host computer 1 and sends an identify message, followed by sending received data, and subsequently. Good status and command complete message sent to host computer 1
Sent to. Then S between both devices 1, 2
The CSI bus will be bus-free again. With the above, the data receiving operation is completed.

[0025]

As is apparent from the above description, according to the present invention, since the asynchronous notification to the initiator is performed by the reselection operation for the get message command, the problems associated with the polling operation can be solved. Further, by separating the asynchronous notification process and the data reception process, it is possible to save the time for allocating the data to the memory of the host computer forming the initiator and improve the processing efficiency of the host computer. Furthermore, by waiting for the communication device that constitutes the target in the ring state, there is no loss time in data communication and the processing efficiency on the communication line can be improved, resulting in a communication error (timeout).
Various effects can be obtained such as eliminating the danger of.

[Brief description of drawings]

FIG. 1 is a diagram showing a time chart according to a first embodiment of a communication method of a SCSI system according to the present invention.

FIG. 2 is a diagram showing a time chart according to a second embodiment of the communication method of the SCSI system according to the present invention.

FIG. 3 is a diagram showing a time chart according to a third embodiment of the communication method of the SCSI system according to the present invention.

FIG. 4 is a block diagram showing a hardware configuration of a SCSI system to which the present invention is applied.

FIG. 5 is a diagram showing a time chart of an example of a communication method of a conventional SCSI system.

FIG. 6 is a diagram showing a time chart of another example of the communication method of the conventional SCSI system.

[Explanation of symbols]

 1 Host computer (initiator) 2 Communication device (target) 3 Communication line 4 SCSI bus

Claims (3)

(57) [Claims] 1. In a system in which a plurality of SCSI devices serving as an initiator and a target are connected to a SCSI bus,
A communication method for a SCSI system, wherein when a response is returned from a target to a command from an initiator, a message sending operation for asynchronous notification is added to perform asynchronous notification. 2. In a system in which a plurality of SCSI devices serving as an initiator and a target are connected to a SCSI bus,
A communication method for a SCSI system characterized in that, when a command is sent from an initiator to a target, a command sending operation for asynchronous notification is added to perform asynchronous notification and data reception separately for each command. 3. In a system in which a plurality of SCSI devices serving as an initiator and a target are connected to a SCSI bus,
The SC is characterized by performing an asynchronous notification by providing an operation for sending a message for asynchronous notification from the target to the initiator, regardless of reception of a command sent from the initiator to the target.
Communication method of SI system.