JPH0614327B2 - Input/Output Command Control Method - Google Patents

Description

Detailed Description of the Invention (1) Field of the Invention The present invention relates to a data processing device, and more particularly to an I/O command control method in a channel processing device that does not have an activation queuing mechanism for I/O requests.

(2) Prior Art FIG. 2 shows the system configuration of a conventional data processing system.

2, reference numeral 10 denotes a central processing unit, 11 denotes a channel processing unit, 16 denotes a main storage device, and 14 and 15 denote input/output devices. Reference numeral 12 within the channel processing unit 11 denotes a channel control unit, and 13 denotes a channel.

FIG. 3 is a diagram showing the control timing of signals on a general I/O interface between the channel 13 and the input/output devices 14 and 15. In FIG.

In FIG. 3, the symbolic names of the signals are as follows:

ADR-OUT: Address out SEL-OUT: Select out OPL-IN: Operational in ADR-IN: Address in CMD-OUT: Command out STA-IN: Status in SRV-IN: Service in SRV-OUT: Service out DATA-IN: Data in DATA-OUT: Data out SUP-OUT: Suppress out BUS-OUT: Bus out BUS-IN: Bus in Also, , , , are the signals ADR-OUT, SRV-IN, and SRV-IN, respectively.
indicates the rising edges of EL-OUT, OPL-IN, and SRV-OUT, and indicates the falling edge of the signal SEL-OUT.

In a data processing system as shown in FIG. 2, a central processing unit 10 issues an input/output start command (hereinafter referred to as a start I/O first release command: SIOF command) to a channel control unit 12 in a channel processing unit 11 to request input/output start for an input/output device 14 via a channel 13.

The channel control unit 12 checks the subchannel corresponding to the input/output device 14 and at the same time checks the status of the channel 13 and returns response information to the central processing unit 10 according to that status. The central processing unit 10 then sets a condition code for the SIOF command based on that response information.

At this time, the channel status checked by the channel processing device 11 corresponds to the condition code (CC) for the SIOF command, and is either CC=0, which indicates that the channel is not communicating with any I/O device, CC=1, which indicates that the channel is in a logout pending state, CC=2, which indicates that the channel is communicating with an I/O device, or CC=3, which indicates that the channel is inoperable.

However, when a channel is in the initial startup sequence with a certain I/O device and connection confirmation with that I/O device has not yet been completed (up to just before in Figure 3), the channel does not fall into any of the above channel states. Therefore, in the past, it was common to wait until connection confirmation was completed and then use a hardware implementation method that determines the channel state corresponding to the condition code (depending on the hardware implementation method, the channel state may not be determined until the time in Figure 3).

Therefore, if a SIOF command is issued during a period in which the state of the channel cannot be determined, the channel control unit 12
Since the SIOF instruction cannot immediately return response information to the central processing unit 10, the central processing unit 10 cannot immediately set a condition code for the SIOF instruction.

Generally, when an OS (operating system) receives an I/O interrupt on a certain channel, one of the triggers for issuing a SIOF command on a block multiplexer channel is to select the highest priority I/O start request from among the I/O start requests for that channel and issue a SIOF command, and if the condition code is 0, to subsequently select the next highest priority I/O start request from among the I/O start requests for that channel and issue a SIOF command. This logic is repeated until either there are no more I/O start requests for that channel or a condition code of 2 (channel communication in progress) is returned in response to the issued SIOF command.

Incidentally, in recent years, the processing speed of central processing units has increased significantly, so that the time from when a condition code = 0 is received in one input/output command in the above logic until the next SIOF command is issued has become shorter.

On the other hand, in recent years, inexpensive and easily available microprocessors have come to be used for the interface control sections for channels in input/output control devices, which were previously configured with hard logic. As a result, the time required for interlocking between the channel and the input/output device has increased, and in particular, the time elapsed from point A to point B in Figure 3 has become longer.

As a result, in the above logic, after receiving condition code = 0 in the first SIOF command,
At the time an IOF command is issued, the operation on the I/O interface by the previous SIOF command often has not yet reached the confirmation of the connection between the channel and the input/output device. In this case, as described above, the channel processing unit cannot return the response information of condition code = 2 for the second SIOF command to the central processing unit until it can determine the channel state, so the setting of the condition code is delayed, resulting in the disadvantage that a high-speed central processing unit cannot operate efficiently.

Since the OS covers a wide range of central processing units with different processing speeds, it is not desirable to change the logic of the OS. Therefore, in the above case with a high-speed central processing unit, it is necessary to shorten the time required to return the condition code = 2.

(3) Object of the Invention The object of the present invention is to eliminate the above-mentioned drawbacks in a central processing unit with a high processing speed by returning CC=2 to the next I/O command even when the connection confirmation with the I/O device on the I/O interface by a previously issued I/O command on the same channel has not been completed.

(4) Configuration of the Invention (4-1) Characteristics of the Invention and Differences from Prior Art In a data processing system consisting of a central processing unit, a channel processing unit that manages multiple channels, and multiple input/output devices connected to each channel via an I/O interface, even when the channel of an access path designated by an input/output command (N) issued by the central processing unit is in the process of input/output activation prior to data transfer for an input/output command (M) issued prior to the input/output command (N) and connection confirmation with the input/output device has not yet been completed, the channel processing unit reports the state of the channel to the central processing unit as if communication with the input/output device had already begun, and the central processing unit issues an input/output command (N).
The present invention is characterized in that it sets a condition code to the DMA channel indicating that the channel is communicating with an I/O device.

(4-2) Embodiment of the Invention Fig. 1 shows an embodiment of the present invention, in which 10 is a central processing unit and 11 is a channel processing unit. The channel processing unit 11 comprises a channel control unit 12 and a plurality of channels such as a channel 13. The channel 13 is an I/O
The channel control unit 12 includes a centralized control unit 20, and the channel 13 includes a channel control unit interface control unit 21 and an I/O interface control unit 22.
2, a channel state register 23, and a latch 24.

When the central processing unit 10 issues a SIOF command to the input/output unit 14 via the channel 13, the central processing unit 10 issues a SIOF command to the integrated control unit 2 in the channel control unit 12.
An I/O start request signal 30 is sent to 0.

When the centralized control unit 20 receives an I/O start request signal 30, it checks the subchannel corresponding to the I/O device 14 and communicates with the channel control unit interface control unit 21 in the channel 13 via signal line 32. By learning the contents of the channel status register 23 in the channel 13 via signal line 40, the centralized control unit 20 confirms the status of the channel and reports information on setting the condition code to the central processing unit 10 via a condition code setting signal 31.

The central processing unit 10 receives the condition code setting signal 3
When 1 is received, a condition code for the SIOF command is set, and processing moves to the next command.

The channel status register 23 is a register that indicates the status of the channel 13.
Among the signals taken from the S during the initial startup sequence,
The latch 24 is set to 1 from when the SEL OUT signal becomes 1 until the SEL OUT signal in a report sequence without a command chain designation becomes 0 (between and in FIG. 3). The output of the latch 24 is sent to the channel status register 23 via a signal line 37. The channel status register 23 is connected to the signal line 3
7, an indication is made as to whether the state of channel 13 is busy or not.

For example, when the central processing unit 10 issues a SIOF command to the I/O device 14 via the channel 13, the SIOF command to the I/O device 15 via the channel 13 that was issued just before that is
An I/O operation initiated by an IOF command is in the initial startup sequence on the I/O interface and the OPL
Even if the IN signal is still 0, the SEL OUT
If the signal is 1, the channel state register 23 indicates that channel communication is in progress, and the centralized control unit 20 can immediately report this to the central processing unit 10 via the condition code setting signal 31, so that the central processing unit 10 can set the condition code to 2 and move on to the next command processing. That is, in the above case, the time required to set the condition code to 2 for the SIOF command can be shortened compared to the conventional case.

(5) Effects of the Invention As described above, according to the present invention, even if the channel of the access path specified by an I/O command (N) issued by the central processing unit is in the process of I/O startup before data transfer for the immediately preceding I/O command (M) and connection confirmation with the I/O device has not yet been completed, the channel status can be reported as in communication by the central processing unit, so that a condition code indicating that the channel is communicating with the I/O device can be immediately set for the current I/O command (N), thereby offering the advantage of preventing a decrease in the efficiency of a high-speed central processing unit.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram showing the system configuration of a conventional data processing system, and FIG.
The figure shows the control timing of signals on the I/O interface. In the figure, 10 is a central processing unit, 11 is a channel processing unit,
Reference numeral 16 denotes a main memory device, and reference numerals 14 and 15 denote input/output devices. Within the channel processing device 11, reference numeral 12 denotes a channel control unit, 13 denotes a channel, 20 denotes a centralized control unit, 21 denotes a channel control unit interface control unit, 22 denotes an I/O interface control unit, 23 denotes a channel status register, 24 denotes a latch,
35 is an I/O interface.

Claims (1)

[Claims] [Claim 1] In a data processing system consisting of a central processing unit, a channel processing unit which manages multiple channels, and multiple input/output devices connected to each channel via an I/O interface, an input/output command control method characterized in that, even when the channel of the access path specified by an input/output command (N) issued by the central processing unit is in the process of input/output activation before data transfer for an input/output command (M) issued prior to the input/output command (N) and connection confirmation with the input/output device has not yet been completed, the channel processing unit reports the state of the channel to the central processing unit as if communication with the input/output device had already begun, and the central processing unit sets a condition code for the input/output command (N) indicating that the channel is communicating with the input/output device.