JP2948380B2 - Data communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication device used in a computer system having a SCSI bus.

[0002]

2. Description of the Related Art Conventionally, there is a device having a communication function by connecting a communication adapter to a SCSI bus of a host computer. Here, SCSI (Small Computer System Interface)
Is a standard established by the American National Standard Institute (ANSI). Due to its specifications, commands and data are transferred between an initiator that issues an instruction and a target that receives and executes the instruction.

In a conventional apparatus having a facsimile adapter or the like using such a SCSI bus, a host computer and a communication adapter have a function as a SCSI initiator (a side that issues instructions) and a function as a target (a side that receives instructions). (Japanese Patent Laid-Open No. 3-38163)
No.). Therefore, in the data communication between the host computer and the communication adapter, bidirectional data communication has been realized by transmitting data in each case as the initiator transmitting data and the receiving side as the target.

[0004]

However, many personal computers and workstations used as host computers have only the function of a SCSI initiator. Such personal computers and workstations are used as host computers of the above-mentioned conventional devices. It could not be used. Because, when the host computer has only the function of the initiator and the communication adapter has only the function of the target, the communication adapter as the target notifies the host computer as the initiator that data has arrived from the outside via the communication line. This is because it has a problem that it is difficult to notify the user, and therefore, even if the communication adapter wants to transmit data to the host computer, it cannot transmit the data by itself.

In addition, when a communication adapter is added to an existing computer system having no communication adapter, even if the host computer has a SCSI bus, if the host computer does not have the functions of both the initiator and the target,
There is a problem that it cannot be easily added. This is because, if an existing system in which the host computer has only the function of the initiator is to be used in the conventional method, if the host computer also has the target function, it is necessary to modify or change the hardware or the like so that the host computer also has the target function. Is required, and the remodeling man-hour and cost for that are greatly increased.

In order to solve the above-mentioned problems, the present invention provides a bidirectional data communication using SCSI between a host computer having only a SCSI initiator function and a communication adapter having only a target function. It is intended to provide functions.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a data communication device used in a computer system having a SCSI bus, wherein the data communication device is an SC as a target.
A communication adapter having an SI function and connected to the SCSI bus; and a host computer having a SCSI function as an initiator and connected to the SCSI bus, wherein the host computer is It is characterized in that the communication adapter has means for periodically checking whether or not there is data received from the outside by using a SCSI command.

Further, the host computer may further comprise means for examining the data length when the confirmation means finds that there is data received from outside. The means by which the host computer checks whether there is data to be received by the communication adapter is UNIX (registered trademark).
May be performed in the system call select the target). The communication adapter controls the operation of the communication adapter as a target for the SCSI bus and controls the inside of the communication adapter, a ROM for storing a control program for the CPU, and an external A communication control unit for transmitting and receiving data to and from the host computer, a SCSI control unit for transmitting and receiving data via the SCSI bus with the host computer, and the SCSI control unit and the communication control unit for transmitting and receiving data. It can also comprise a buffer memory for storing data.

[0009]

With the above arrangement, in the data communication apparatus of the present invention, the host computer periodically checks whether or not there is data received from the outside at the communication adapter by using a SCSI command. This allows a host computer with only the function of a SCSI initiator and a SCSI
SCSI between communication adapters with only
, It is possible to perform bidirectional data communication.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one configuration example of the present invention. Reference numeral 1 denotes a host computer, which performs various arithmetic processes and includes storage means such as a hard disk and a memory, and can create, store, and save communication data such as text data and image data. Host computer 1
Has a function as a SCSI initiator.
A SCSI command is sent to the communication adapter 2 via the bus.

Reference numeral 2 denotes a communication adapter, which has a function as a SCSI target, and is provided from the host computer 1.
According to the SCSI command, data of the host computer 1 is transmitted to the outside, or data received from the outside is transmitted to the host computer 1. In order to control these data transfers, the communication adapter 2 has two types of status information using software registers or hardware registers. One is a communication line status, which indicates a state in which data is to be sent to the communication adapter 2 from outside. The other is a SCSI status, which has both reception data bits and transmission data bits. The received data bit indicates that data to be sent to the host computer 1 via the SCSI bus has been received from the outside. The transmission data bit indicates the data to be transmitted to the outside by the host computer 1.
Indicates that it has been received from the SCSI bus.

Reference numeral 3 denotes a SCSI bus to which the host computer 1 and the communication adapter 2 are connected. Reference numeral 4 denotes a communication line connected to the communication adapter 2. FIG. 2 is a block diagram showing a configuration example of the communication adapter 2. 5 is CPU
And controls the operation of the communication adapter as a target for the SCSI bus and controls the inside of the communication adapter.

Reference numeral 6 denotes a ROM for storing a control program for the CPU 5. Reference numeral 7 denotes a communication control unit which transmits and receives data to and from the outside via the communication line 4. Reference numeral 8 denotes a SCSI controller, which has a function as a target, and transmits and receives data to and from the host computer 1 via the SCSI bus 3.
Reference numeral 9 denotes a buffer memory (using a semiconductor memory), which stores data transmitted and received by the SCSI control unit 8 and data transmitted and received by the communication control unit 7. The buffer memory 9 may use a semiconductor memory, or may be a hard disk or other storage means.

FIG. 3 shows a flow on the host computer 1 side when data is transmitted from the communication adapter 2 to the host computer 1. The host computer 1 has data received from the outside on the communication adapter 2. Means for confirming whether or not there is data received from the outside by the confirming means;
4 shows a procedure including means for checking the data length.

The operation of transmitting data from the communication adapter 2 as the target to the host computer 1 as the initiator in the embodiment of the present invention configured as described above will be described with reference to the drawings. First, the host computer 1 checks whether data to be received is present in the communication adapter 2 (S31 in FIG. 3). As one of the realization methods, the host computer 1 transmits the SCSI command TEST U
Send NIT READY (see the command list in Table 2) to the communication adapter 2. SCSI targets usually return status for SCSI commands. Table 1 shows a list of the statuses.

[0016]

[Table 1]

[0017]

[Table 2]

In response to the TEST UNIT READY command, the communication adapter 2 of this embodiment returns GOOD when there is no data to be received by the host computer 1, and
When there is data to be received by the host computer 1, the CONDITION MET is returned as the status (see FIG. 8 for the internal processing of the communication adapter 2 for returning the status). Can be confirmed.

The operation of returning a status from the communication adapter 2 in response to a SCSI command from the host computer 1 is performed by interrupt processing inside the communication adapter 2. This interrupt processing will be described with reference to the flow of FIG. If the communication adapter 2 is selected as a SCSI target, the SCSI controller 8 in the communication adapter 2
An interrupt occurs for PU5 (S81). In this interrupt processing, the command is executed in response to a SCSI command from the host computer 1 (S82). For example, in response to the TEST UNIT READY command, if the received data bit of the SCSI status inside the communication adapter 2 is “0”, there is no data to be received by the host computer 1, and the status GOOD is returned. If "1", if there is data to be received by the host computer 1, the status is CONDITION ME
Returns T.

Then, the CPU 5 executes the command in response to the SCSI command, and determines whether the SCSI command is a command accompanied by data transfer (S8).
3) If the command is only status and does not involve data transfer like the TEST UNIT READY command, the interrupt processing is terminated (S87). If the command involves data transfer, the SCSI command from the host computer 1 is sent. Is determined (S84). If the data transfer is from the host computer 1 to the communication adapter 2, the transmission data bit of the SCSI status is set to "1" (S85).
If the data has been transferred, the received data bit of the SCSI status is set to "0" (S86).

The operation of the communication adapter 2 for transmitting data received from the outside to the host computer 1 will be described with reference to the flow chart shown in FIG. The communication adapter 2 is reset when the power is turned on (S91), and clears the communication line status and the SCSI status (S9).
2). Next, the communication status is read, and it is checked whether the status is "data reception status" indicating the state of sending data from the communication line 4 (S93). The data is transferred to the buffer memory 9, and the communication line status is cleared (S94). Further, the received data bit of the SCSI status is set to "1" (S95), and the process waits until the received data bit of the SCSI status becomes "0" in the interrupt processing shown in FIG. 8 (S96). If the received data bit of the SCSI status becomes "0", it is checked whether or not the transmission data bit of the SCSI status is "1" (S97). If the transmission data bit of the SCSI status is "1", since the data sent from the host computer 1 by the SCSI command exists in the buffer memory 9, the data is transferred from the buffer memory 9 to the communication control unit 7, and The transmission data bit of the status is set to "0" (S98). Then, the communication line status is checked again (S93), and the above processing is repeated.

The host computer 1 issues the SC issued by itself.
When the status from the communication adapter 2 with respect to the SI command is received, if the status from the communication adapter 2 is GOOD, there is no data to be received by the host computer 1, so the host computer 1 sends the SCSI command again at regular intervals. Execute TEST UNIT READY (S
31). That is, while there is no data to be received by the host computer 1, this (S31) is repeated periodically. This cycle is 900 ms in this embodiment, which is determined by the data transfer speed of the communication line 4 and the capacity of the buffer memory 9.

If the status from the communication adapter 2 is CONDITION MET, there is data to be received by the host computer 1. Is checked (S32). The reason for checking the length is the SCSI command GET MESSAGE for the host computer 1 to receive data from the communication adapter 2 (see Table 2).
Has the command format shown in Fig. 4. GET MESSAG
This is because the use of E requires information on the length of the data to be received. In this embodiment, a vendor unique command GET DATA SIZE is used as a means for checking the data length. FIG. 5 shows the command format of the GET DATA SIZE, and FIG. 6 shows the data format. Command format SCSI shown in Fig. 5
The host computer 1 issues the command GET DATA SIZE
When sent to the communication adapter 2, the communication adapter 2 sends data to the host computer 1 in the data format shown in FIG. This allows the host computer 1 to know the length of the data to be received.

Next, the host computer 1 sends a SCSI command GET MESSAGE (6) in the command format shown in FIG. 4 to the communication adapter 2 (S33). Upon receiving this, the communication adapter 2 sends data of the length specified by GET MESSAGE (6) to the host computer 1, and the host computer 1 finishes receiving data from the communication adapter 2. By the way, in this embodiment, the TEST UNIT READY command is used as a means for confirming the data arrival of the communication adapter 2, but a command not shown in Table 2 is newly created for the communication adapter 2 (called a vendor unique command). , It can also be used to check the state of incoming data. Also,
Although the host computer 1 used the SCSI command GET MESSAGE (6) (see Table 2) for receiving data from the communication adapter 2, it is also possible to create and use a vendor unique command. Is GET M
If a command such as ESSAGE (6) that does not need to specify a data length is created, the host computer 1 does not need to check the length of data received from the communication adapter 2 (S32), and S32 can be omitted.

When the OS of the host computer 1 is UNIX,
FIG. 7 shows how the processing shown in FIG. 3 is realized. Figure 7 shows the UNIX corresponding to the processing in the user program
Indicates kernel (device driver) processing. At the user program level, first, a system call select () is called to check whether data received by the host computer 1 exists in the communication adapter 2. Upon receiving this system call, the UNIX kernel calls the select entry (here, xxselect) of the device driver (U71). In the xxselect entry, the SCSI command
Execute TEST UNIT READY for communication adapter 2, and if the status of communication adapter 2 is GOOD, repeat TEST U
Execute NIT READY (K72). If the status of communication adapter 2 is CONDITION MET, xx
select returns 1 as a return value (K73).

When the system call select () is completed, the user program calls the system call ioctl () with a command for checking the length of the data to be received (U74). In response to this system call, the UNIX kernel sets the device driver ioctl entry (here, xx
ioctl) (K75). In the xxioctl entry, the SCSI command GET DATA SIZE is executed for the communication adapter 2, and the data length received from the communication adapter 2 is passed to the user program (K76).

Next, in order to receive data of the checked length,
The user program calls the system call "read" (U77). In response to this system call, the UNIX kernel reads the device driver's read entry (here, xxread
), And in the xxread entry, GET MESSAGE of the SCSI command is executed for the communication adapter 2, communication data is received from the communication adapter 2 (K78), and this is passed to the user program (U79).

The data transmission from the host computer 1 to the communication adapter 2 is performed by transferring data from the initiator to the target.
Confirms that the SCSI bus is not used, and executes the data transmission SCSI command SEND MESSAGE (see Table 2). This data transmission is performed by the OS of the host computer 1.
The case of UNIX will be described. The user program calls the system call write () to send the data. In response to this system call, the UNIX kernel writes the write entry of the device driver (here, xxwrit
e)). In the xxwrite entry, check the status flag of the SCSI bus managed in the device driver, and if the SCSI bus is available, use the SCSI command SEND MESSA.
Execute GE for the communication adapter 2 and send communication data to the communication adapter 2.

In the above embodiment, the TEST UNI
If the communication adapter 2 has data to send to the host computer 1 in response to T READY, the CONDITION MET is returned as the status, but the Reserved bit of GOOD is set to 1
It is also possible to set the status described above or a code other than those described in Table 1 as the status.

[0030]

As described above, according to the present invention, even when the host computer has only the function of the initiator and the communication adapter has only the function of the target, the host computer can communicate with the target communication adapter from the outside. The host computer, which is the initiator, can easily know that the data has arrived via the line. Therefore, whenever the target communication adapter needs to transmit data to the host computer, it can transmit the data to the host computer.

When a communication adapter is added to an existing computer system having no communication adapter, the host computer has a SCSI bus,
Although there is no function of both the initiator and the target, as long as it has the function of the target, there is an effect that the present invention can be easily implemented only by adding or changing a user program on the host computer side. Especially when the host computer OS is UNIX, most of the processing required by the UNIX kernel is taken in. Therefore, once the UNIX kernel is changed, it is extremely easy to change or add the user program itself thereafter. Become.

In this manner, bidirectional data communication can be performed between a device having only an initiator and a device having only a target on the SCSI bus.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a data communication device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a communication adapter according to the embodiment.

FIG. 3 is a flowchart showing a control procedure of the host computer of the embodiment.

Fig. 4 Command format of SCSI command GET MESSAGE (6)
(SCSI standard).

FIG. 5 is a command format of the SCSI command GET DATA SIZE of the embodiment (unique to the present invention).

FIG. 6 shows a data format of the SCSI command GET DATA SIZE of the embodiment (unique to the present invention).

FIG. 7 is a control procedure in which the OS of the embodiment is UNIX.

FIG. 8 is a flowchart showing an interrupt process in the communication adapter of the embodiment.

FIG. 9 is a flowchart showing a control procedure in the communication adapter of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Host computer 2 Communication adapter 3 SCSI bus 4 Communication line 5 CPU 6 ROM 7 Communication control unit 8 SCSI control unit 9 Buffer memory

Claims (4)

(57) [Claims] [Claim 1] SCSI (Small Computer System Interface)
e) a data communication device used in a computer system having a bus, the communication adapter having a SCSI function as a target and connected to the SCSI bus, and the SCSI having a SCSI function as an initiator. A host computer connected to a bus, wherein the host computer has means for periodically confirming whether or not there is data received from outside in the communication adapter using a SCSI command. A data communication device characterized by the above-mentioned. 2. The apparatus according to claim 1, wherein said host computer further comprises means for examining the data length when said confirming means determines that there is data received from outside. Data communication device. 3. The data communication apparatus according to claim 1, wherein the means for checking whether or not there is data to be received by the communication adapter by the host computer is executed by a UNIX system call select. 4. The communication adapter controls the operation of the communication adapter as a target for the SCSI bus and controls the inside of the communication adapter.
A CPU, a ROM for storing a control program of the CPU, a communication control unit having a communication line for transmitting and receiving data to and from the outside, and having a function as a target, and transmitting data via the host computer and the SCSI bus. 3. The data communication device according to claim 1, further comprising: a SCSI control unit that performs transmission and reception; and a buffer memory that stores data transmitted and received by the SCSI control unit and the communication control unit.