JPH06314251A - Scsi data transfer device - Google Patents

Abstract

PURPOSE:To provide a data transfer device which transfers mass data from a host to a target device (CD-WO) through a SCSI bus without being influenced by a transferring state or transfer rate from the host. CONSTITUTION:The SCSI data transfer device 1 is constituted of a first SCSI interface 4 for input, a second SCSI interface 5 for output, a buffer memory 3, and a processing part 2 to DMA(direct memory access)-control independently an input side and an output side. The data SCSI-inputted from the host (computer) 8 is DMA-transferred to the buffer memory 3 through the first SCSI interface 4. The data to be SCSI-outputted to an external (SCSI) device 10 is DMA-transferred from the buffer memory 3 through the second SCSI interface 5. The SCSI-inputted transferred data is divided into the command and the data of SCSI, and only the data of SCSI is stored in the buffer memory 3, and is transferred.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SCSI data transfer suitable for data transfer between a host computer and an external device having a SCSI interface, and particularly for data transfer to an external device such as a CD-WO (Write Once) or printer. It relates to the device.

[0002]

2. Description of the Related Art In data transfer via a SCSI bus, a host computer 23 is conventionally connected to a data transfer device (buffer device) 22 having a SCSI interface 20 and a buffer memory 21, as shown in FIG. Connected to the SCSI bus 24, the transfer data from the host is stored in the buffer via the SCSI bus 24, and then transferred to the external SCSI device (target device) 25 connected to the same SCSI bus 24. Was configured to do.

[0003]

[Problems to be Solved by the Invention] Such a conventional SC
The SI-compatible data transfer device 22 has only one SCSI interface (port) 24 as an input / output interface. Therefore, when data from the host is received via the SCSI bus and buffered before being transferred to the target device, the transfer timing is greatly affected by the state of the SCSI bus to which the host is connected. Therefore, for example, C
When it is necessary to transfer data continuously and at a constant speed without interruption, such as D-WO (Write Once) or a printer, there is a problem that the transfer cannot be realized correctly even if the transfer data is buffered. Occurs.

Further, in the conventional SCSI-compatible data transfer device, all the data transferred from the host is buffered, and then the data is transferred to the target device on the SCSI bus. Therefore, when transferring a large amount of data larger than the size of the buffer from the host, it is necessary to store the data in the buffer and transfer the data to the device a plurality of times, which causes a problem that the transfer data is interrupted each time.

[0005]

In order to solve the above problems, the present invention provides a host (computer) 8 having a SCSI interface 11 as shown in FIG.
External (SCS with SCSI interface 12
I) SCSI bus to device 10 (7 and 9)
A SCSI data transfer device (1) for transferring data via a first SCSI interface (4) for input,
It is composed of a second SCSI interface 5 for output, a buffer memory 3, and a processing unit 2 for independently controlling a DMA (Direct Memory Access) on the input side and the output side. Command and data, and only the SCSI data is stored in the buffer memory, and the SCSI input from the host and the SCSI output to the external device are independently D
The present invention provides a SCSI data transfer device characterized by performing MA transfer.

[0006]

According to the SCSI data transfer device 1 configured as described above, the SCSI data is transferred from the host (computer) 8 to the SCSI device.
The input data is DMA-transferred to the buffer memory 3 via the input first SCSI interface 4, and the data output to the external (SCSI) device 10 via the SCSI is output to the second SCSI interface 5 for output. DMA transfer is performed from the buffer memory 3 via the above.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS SCSI (Small Computer Sys
tem Interface) One embodiment of the data transfer device,
This will be described below with reference to the drawings. FIG. 1 is a block diagram of a SCSI data transfer device, and FIG. 2 is a diagram for explaining the operation of a buffer memory of the SCSI data transfer device.

As shown in FIG. 1, the data transfer device 1 is
Central processing unit 2 having independent DMA (Direct Memory Accese) controller function of two channels (channel 1 and channel 2 described later) 2, buffer memory 3 for storing transfer data (only data), first input / output SCSI interface (controller) 4, second
The input / output SCSI interface (controller) 5 is used. The central processing unit 2, the buffer memory 3, and the input / output interface SCSI controllers 4 and 5 are connected via an internal bus 6. The buffer memory 3 is a ring-shaped memory as will be described later.

In this data transfer device 1, the SCSI interface 4 for the first input / output is the first SCS.
Connected to the host computer 8 via the I-bus 7,
In order for the transfer data from the host computer 8 to be transferred to the buffer memory 3 by DMA, the second input / output SCSI interface 5 is further provided with a second SCSI bus 9.
Via external SCSI device (eg CD-WO)
10 is connected to the buffer memory 3 and the transfer data from the buffer memory 3 is DMA-transferred to the external SCSI device 10. The host computer 8 and the external SCSI device 10 have built-in SCSI interfaces (controllers) 11 and 12 for input / output.

Next, the operation of the data transfer device configured as described above will be described. The data transferred from the host computer 8 via the SCSI bus 7 is taken into the internal data bus 6 by the SCSI interface (controller) 4 on the input side of the data transfer device 1 and stored in the buffer memory 3. At this time, the input transfer data is divided into SCSI commands and data, and only the SCSI data is stored in the buffer memory 3. Under the control of the central processing unit 2, the stored data is transferred to the external SCSI device 12 together with a command of a new SCSI command via the output-side SCSI interface (controller) 5. The control of this data transfer can be freely changed by a program executed by the central processing unit 2. This point will be described in detail below.

In the SCSI transfer from the host computer 8, when the SCSI command is a write command, the data transferred from the host computer 8 in the data phase is transferred to the channel 1 DMA through the SCSI interface (controller) 4 on the input side. Internal data bus 6 under the control of the controller
And is stored in the buffer memory 3. Then, after a certain amount of data is accumulated, the accumulated data is controlled by the DMA controller of channel 2 so that the accumulated S
From the buffer memory 3 through the CSI interface (controller) 5 to the external S which is the target device
It is transferred to the CSI device 12.

The operation of the data transfer pointers of the input section and the output section at this time is shown in FIG. In FIG. 2, the ring indicates a buffer (buffer memory 3), the size of which is 0.
It is one round from to MAX. The shaded area inside the ring indicates the accumulated transfer data. An arrow Pa indicates an output read pointer from the buffer memory 3 to the target device (external SCSI device 12), and an arrow Pb indicates an input write pointer from the host (host computer 8) to the buffer memory 3. Also, the arrow m
Indicates the traveling direction of the two pointers Pa and Pb.

First, data is transferred from the host to the buffer from the 0 address to half the capacity of the buffer. Then, the transfer from the buffer to the target device is started. At this time, the input from the host to the buffer is continuing. The transfer rate from the host to the buffer is faster than the transfer rate from the buffer to the target device, so the transfer from the buffer to the target device is performed by reading the data transferred from the host to the buffer in order. By continuing the above, it is possible to realize data transfer exceeding the buffer capacity. However, conversely, the transfer from the host to the buffer may catch up with the transfer from the buffer to the target device, that is, the arrow Pb may exceed the arrow Pa in FIG. When it becomes smaller than a certain value, DMA transfer from the host to the buffer is made to wait.

Thus, the input and output SCSI
With regard to the transfer at the port, data is transferred to the output side at a constant speed without interruption by two independent DMA transfers. That is, since two independent SCSI ports are provided as input / output interfaces, the transfer data from the host can be transferred to another SCSI device regardless of the transfer speed or state. With the above function, C can be used even from a host that has a multitasking OS.
It becomes possible to transfer data to a D-WO or a printer at a constant speed without interruption. The input / output SCSI ports (interface, controller) are controlled by an independent programmable DMA controller, so the transfer rate and protocol can be changed freely, so it can be used for various peripheral devices with a SCSI interface. Can be used.

[0015]

As described above in detail, according to the data transfer apparatus of the present invention, a large amount of data from the host can be transferred to the S
When the data is transferred to the target device via the CSI bus, the data can be transferred continuously without being affected by the transfer state or speed from the host. Data can be reliably transferred to a target device such as a printer.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a data transfer device according to the present invention, and is a configuration diagram of a SCSI data transfer device.

FIG. 2 is a diagram illustrating an operation of a buffer memory (memory managed in a ring shape) of the SCSI data transfer device.

FIG. 3 is a diagram showing a conventional configuration example in which data from a host is buffered and transferred to a SCSI device by using a conventional technique.

[Explanation of symbols]

1 data transfer device 2 central processing unit (DMA controller) 3 buffer memory (ring memory, buffer) 4 first I / O SCSI interface (controller) 5 second I / O SCSI interface (controller) 6 internal Bus 7 First SCSI bus 8 Host computer (host) 9 Second SCSI bus 10 External SCSI device (target device)

Claims (1)

[Claims] 1. A SCSI for transferring data between a host having a SCSI interface and an external device having a SCSI interface via a SCSI bus.
A data transfer device, wherein a first SCSI interface for input, a second SCSI interface for output, a buffer memory, an input side and an output side are independently DMA (direct transfer).
(Memory access) controller processing unit, which divides the input transfer data into SCSI commands and data, stores only SCSI data in the buffer memory, and inputs SCSI from the host and inputs to external devices. A SCSI data transfer device characterized in that DMA output is independently performed for SCSI output.