JPH0256042A - Data transfer requesting system - Google Patents

Abstract

PURPOSE:To prevent a data overrun to a buffer storage of an in-device channel, and also, to freely set the length of a transfer cable irrespective of the capacity of a buffer by designating the number of bytes of transfer request data. CONSTITUTION:When a command CNCT from an in-device channel 11 is received, a remote channel 10 starts an input/output device 9. Also, when a data transfer request command DRQ is received, a response SST is transmitted to the in-device channel 11, and read data by the number of bytes designated by the command is transferred to the in-device channel 11. When this command is received, the remote channel 10 sets the number of request bytes to a data byte counter DBC. When the number of bytes is set to the counter DBC, a data transfer control part 16 reads the data from a data buffer 15, and transfers the data to the channel 11.

Description

[Detailed Description of the Invention] [Summary] A method for transferring read data from a channel within the main unit to a channel within the main unit from a remote channel that controls an input/output device installed remotely from the main unit of the system. Regarding the data transfer request method, the data request command with the requested number of bytes is sent from the internal channel, and the remote channel transfers data within the range of the requested number of bytes, thereby preventing data overruns. In a computer system that uses an input/output control method, an input/output device installed remotely from the main unit of the system, a remote channel that controls the transfer of input/output data of the input/output device, and a The device is configured to have an internal channel within the main device that indicates the number of bytes requested for data transfer to the remote channel when transferring data from the input/output device.

[Industrial application field]

The present invention relates to an input/output data transfer control method in a computer system using a channel control method. This invention relates to a method for requesting data transfer from a channel within the main device when transferring read data to.

When installing an input/output device remotely from the main frame of a computer system, the limit distance was up to about 120 m when using conventional electrical parallel interfaces, but when using recent serial interfaces using optical signals, the maximum distance is about 2 km. It became possible to extend the For this purpose, for example, a channel with a bidirectional conversion function between an electrical parallel interface and a serial interface using optical signals is connected to an input/output device installed remotely on a campus-sized scale, and this channel is connected to a channel in the mainframe. A method of transferring data between an input/output device and a main storage device in a mainframe by connecting them with an optical cable etc. [Problems to be solved by conventional technology and invention] FIG. 6 shows the connection form between the input/output device, the remote channel (RCH), and the internal channel (CH) of the main device. In the figure, an input/output device 1 and a remote channel 2 are connected by an electrical parallel interface 3, and a remote channel 2 and an internal channel 4 are connected by serial interfaces 5a and 5b using optical signals.

Here, the electrical parallel interface 3 between the input/output device 1 and the remote channel 2 is generally 3MByte
/s, and the serial optical interface between remote channel 2 and internal channel 4 is, for example, 9MByte.
It has a data transfer rate of /s.

When data from the input/output device 1, such as a magnetic tape, is transferred as read data from the remote channel 2 connected to the internal channel 4 as shown in FIG. Data is transferred at an effective transfer rate of 3 MByte/s determined by interface 3, but when the data buffer in device channel 4 runs out of free space, for example, device channel 4 sends a transfer suppression instruction to remote channel 2. , In response to this instruction, the remote channel 2 takes a method of suspending data transfer until the suppression is released.

A method of controlling data transfer to the intra-device channel 4 will be explained with reference to FIG. In the same figure, when read data can be received, the internal channel (CI) 4 instructs the remote channel (RCH) 2 to indicate "ready" indicating that data can be received, and by this instruction, the remote channel (RCH) 2
transfers the read data to internal channel (CH) 4. For example, when there is no free space in the data buffer, internal channel 4 instructs remote channel 2 to suppress data transfer, remote channel 2 suspends read data transfer until it receives a ready instruction from internal channel 4 again,
Ineffective dummy data continues to flow in order to synchronize the serial interface 5b.

In the data transfer control system as shown in FIG. 7, even if the internal channel 4 issues an instruction to suppress data transfer to the remote channel 2, there is a time delay before the remote channel 2 receives the instruction. A major cause of this time delay is the delay due to the cable length. For example, if this delay is 5 ns/m and the cable length is 1 km, the delay time is 5 μs.

If there is such a time delay, depending on the capacity of the buffer in the intra-device channel 4, there is a possibility that data overrun to the buffer will occur when data transfer is interrupted and resumed. This data overrun will be explained with reference to FIG. Figure (a) shows the state when data transfer is suppressed, and there is an empty area in the buffer memory 6 of the internal channel 4, while the read data from the input/output device 1 is in the buffer memory 7 of the remote channel 2, and the data transfer is interrupted. If the transfer suppression time is long, read data is stored in the entire area.

At this point, when data transfer suppression is released as shown in FIG.
The signal is sent to the internal channel 4 side of the device via the serial optical interface. Buffer storage 6 for internal channel 4
If there is less free space in the buffer memory 6, more data than fills the entire area of the buffer storage 6 will be sent, causing a data overrun. In this case, a data overrun error should be notified to the software, but since a data overrun can only be notified to the software by input/output device 1, it is not notified as an interface control check (ICC), which is an interface error. Ru.

In order to prevent data overruns, the buffer memory 6 of the internal channel 4 must have a free capacity larger than the capacity 1 of the buffer memory 7 of the remote channel 2 at the time data transfer suppression is released. If this condition is not satisfied, there is a problem in that the cable length of the serial signal interface connecting both channels is limited.

An object of the present invention is to prevent data overrun by sending a data request command to which a requested number of bytes is added from an internal channel, and by transmitting data within the range of the requested number of bytes from a remote channel.

[Means to solve the problem]

FIG. 1 shows a block diagram of the principle of the present invention. In the figure, the input/output device 9 is installed at a remote location from the main unit 8 of the computer system, for example, at a separate location within the premises.

The remote channel 10 is connected to the input/output device 9 by a parallel interface, for example an electric cable, and controls the transfer of input/output data of the input/output device 9.

An intra-device channel 11 in the main device 8 receives data transferred from the input/output device 9 under the control of a remote channel 10;
That is, at the time of read data transfer, for example, the number of data transfer request bytes corresponding to the free capacity of the buffer storage in the internal channel 11 is instructed to the remote channel IO.

[For production]

In FIG. 1, before and during the start of read data transfer from the input/output device 9 to the main device 8 side, the empty space 1 of the buffer storage from the internal device channel 11 to the internal device channel 11
For example, a data transfer request command with the requested number of bytes added thereto is sent to the remote channel 10. Read data from the input/output device 9 is transferred from the remote channel 10 within the range of this requested number of bytes.

As described above, according to the present invention, read data is transferred within the requested number of bytes of the intra-device channel 11, so data overrun to the buffer storage of the intra-device channel 11 is prevented.

〔Example〕

In-device channel 1 using the transfer data request method of the present invention
A basic configuration block diagram of the remote channel 10 and the remote channel 10 is shown in FIG. In the figure, an internal channel 11 is connected to a data buffer 12, a data transfer control section 13, and a command input/output control section 14, and a remote channel 10 is connected to a data buffer 15, a data transfer control section 16, and a command input/output control section 17. , and a transfer request data number counter 18, both channels 10.11 being connected by a serial signal interface 19.20.

In FIG. 2, an internal channel 11 sends a data transfer request command to which a data request byte number corresponding to the free capacity of an internal data buffer 12 is added from a command input/output control unit 14 to a remote terminal via a serial signal interface 20. Send to channel 10. The remote channel 10 receives this command by the command input/output control unit 17, sets the data transfer request byte number added to this command in the transfer request data number counter 18, and stores the data in the range of this requested byte number in the data buffer. 15 to the serial signal interface 19 under the control of the data transfer control unit 16.
The data is transferred to the intra-device channel 11 via.

An example format of a data transfer request command (DRQ) sent from the intra-device channel 11 to the remote channel 10 is shown in FIG. Data transfer request command (
DRQ) consists of, for example, 2 bytes as a whole, the upper 1 byte is a data request code (DRQC) as an interface command code, and the lower 1 byte is a data byte count (DBC) indicating the number of bytes requested for data transfer. .

FIG. 4 shows a data transfer sequence in the embodiment.

When the internal device channel 11 receives a command from the central control unit (CPU) in the main device 8, it executes a channel command word (CCW) fetch, and when it determines that the command is correct, sends a start command to the remote channel 10. Send CNCT (:]Nect.). Next, the internal channel 11 sends a data transfer request command (
DRQ) to the remote channel IO.

When the remote channel 10 receives the command CNCT from the internal channel 11, it sends the connected input/output device 9,
For example, start a magnetic tape. Also, upon receiving the data transfer request command (D
Read data corresponding to the number of hides specified by RQ) is transferred to the internal channel 11 of the device.

Here, the number of data bytes that can be requested by one data transfer request command (DRQ) includes 10 remote channels.
An upper limit is set in relation to the capacity of the transfer request data number counter 18, and the upper limit value is, for example, 255 Byte. Another data transfer request command (DRQ)
It is assumed that the intra-device channel 11 can transmit the next transfer request command even if the data transfer of the requested number of bytes is not completed.

FIG. 5 shows a block diagram of the configuration of the transfer request data number counter. In the same figure (al indicates the configuration of the transfer request data number counter 18 in the remote channel 10 of FIG. 2, and in the same figure (bl indicates the counter in the internal channel 11 not shown in FIG. 2).

As described above, read data transfer is started by sending a data transfer request command (DRQ) from the command input/output control section 14 of the internal channel 11 to the remote channel 10 in FIG. Is remote channel 10 receiving this command on the command input/output side? When received by the tl1 section 17, the fifth
The requested number of bytes is set in the data byte counter (DBC) 22 via the adder (ADD) 21 shown in FIG.

The initial value of the data byte counter (DBC) 22 is °
Set it to 0゛.

When the number of transfer requested data bytes is set in the data byte counter (DBC) 22, the data transfer control unit 1 shown in FIG.
6 reads data from the data buffer 15 and transfers the data to the internal channel 11 via the serial interface 19. At this time, the data transfer control unit 16 decrements the count value of the data byte counter (DBC) 22 in FIG. 5 every time it sends one byte of data, and continues data transfer until the count value becomes "0".

As mentioned above, the device internal channel 11 can send the next request command before the data transfer of the number of bytes requested by the data transfer request command (DRQ) is completed, but in this case, the addition shown in FIG. The number of requested data bytes is added via the ADD device (ADD) 21, and data transfer continues.

FIG. 5 (bl is a block diagram of a transfer request data number counter for monitoring whether data of the Hyde number requested on the intra-device channel 11 side has been transferred).

The internal channel 11 in the device is the command input/output control unit 1 in FIG.
When transmitting a data transfer request command (DRQ) from 4 to the remote channel 10, the number of requested bytes is added to the data byte counter (ADD) 23 in FIG.
DBC) set to 24. and remote channel 10
Every time one byte of REET data is received from the data transfer controller 13, the data byte counter (DBC) 24 decrements the count value. As a result, the count value of the data byte counter (DBC) 24 indicates the number of bytes of data that has not yet been transmitted out of the data requested to be transferred. As mentioned above, on the device channel 1 side, this data byte counter (DBC) 2
The count value of 4 is controlled so as not to exceed the maximum value '255'.

〔Effect of the invention〕

As described in detail above, according to the present invention, by specifying the number of bytes of transfer request data, it is possible to prevent data overrun into the buffer storage of the internal channel, and to connect the internal channel and the remote channel. It becomes possible to freely set the length of the connecting cable regardless of the buffer capacity.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a basic configuration block diagram of internal channels and remote channels, Fig. 3 is a diagram showing an example format of a data transfer request command (DRQ), Fig. 4 5A and 5B are block diagrams showing the configuration of the transfer request data counter, and FIG. 6 is a diagram showing the connection form of the input/output device, remote channel, and internal channel. 7 is a diagram showing a data transfer control method to an internal channel in the device, and FIG. 8 (81, (b) is an explanatory diagram of data overrun to an internal channel in the device. 1.9...I/O device , 2.10...Remote channel, 4.11...Internal channel, 12.15...Data buffer, 13.16...Data transfer control section, 14.17...Command input/output control Part, 18...Transfer request data number counter

Claims (1)

[Claims] In a computer system using an input/output control method using channels, an input/output device (9) installed remotely from a main unit (8) of the system, and input/output of the input/output device (9). a remote channel (10) for controlling the transfer of data; and said input/output device (9) via said remote channel (10).
A data transfer request method characterized by comprising an intra-device channel (11) in the main device (8) that instructs the remote channel (10) about the number of bytes requested for data transfer when transferring data from the main device (8).