JPS6269349A - Input and output interface - Google Patents

Abstract

PURPOSE:To eliminate an undesired overruns by informing an input/output controller that the data remaining in a data buffer of a channel or an idle area is smaller than the prescribed value and interrupting the transfer of data by the input/output controller when it receives said information. CONSTITUTION:A data buffer control circuit 19 delivers the number of idle data buffers and compares this output with the output of a register 20 set previously through a comparator 21. When the number of idle buffers is smaller than the set number, a signal line 6 (the 3rd control line) is set at logic '1' via a driver circuit 14. While the line 6 is set at logic '0' when the data in the buffer if processed and the number of idle buffers is larger than the set number. That is, the setting action of the control signal 4 is discontinued temporarily to an input/output controller 2 by transmitting the previous announcement signal to the controller 2 before an overrun is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an input/output interface, and more particularly to an input/output interface between a channel and an input/output controller in a data transfer system.

2. Description of the Related Art Conventionally, there has been an input/output interface system in which a channel supplies data to a data bus or takes in data from a data bus in response to a control signal from an input/output control device. ' is proposed in the specification.

Problems to be Solved by the Invention In the input/output interface method described above, the control signals on the interface are not interlocked, so when controlling data transfer of a peripheral device that simulates recording on a rotating medium such as an electronic disk, This method has the disadvantage that data overruns and data underruns that do not physically occur occur, and that time is wasted for recovery processing.

The present invention has been made in order to eliminate the above-mentioned drawbacks inherent in the prior art. Therefore, an object of the present invention is to provide a third control line from the channel to the input/output control device in the above-mentioned interface, and to connect the channel to the input/output control device. in the data buffer,
Compare the number of received data or the number of receivable data with a preset value, energize the third control line if the number is small, and deenergize the third control line when the condition is canceled. However, by interrupting the energization of the first control line between the energization of the third control line and the deactivation of the third control line of the input/output control device, the occurrence of data overrun and data underrun described above can be suppressed. The objective is to provide a new input/output interface that enables

Means for Solving the Problems In order to achieve the above object, the input/output interface according to the present invention includes a channel, an input/output ftdJ control device, and first, second, and third interfaces that connect these devices. The channel includes a control line and a data bus line, and the channel compares the number of remaining data in the data buffer or the number of receivable bytes with a preset value, and energizes the 70th control line while the comparison result is small. The input/output control device has means for analyzing the energization of the first fft control line during the energization of the third control line.

Embodiment Next, a preferred embodiment of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. In the figure, one embodiment of the present invention includes a channel/, an input/output control device, a data bus line 3 connecting these devices, an input strobe signal line (first control line), an output strobe signal line ( No. 1 control line)! , and an input/output interface including a VfT instruction signal line (third control line) 6 during data transfer.

FIG. 2 is a block diagram showing one embodiment of the channel. In Figure 2, channels / are receiver circuits // and /
Driver circuit/3. /G and /S1 Latch circuit /6 and /7, AND-OR gate 2, AND gate 3
, data buffer/1. It includes a data buffer control circuit 'arn, which outputs the number of remaining data in the data buffer or the number of data that can be received by the data buffer, a comparison count register J1, and a comparison circuit 2/.

FIG. 3 is a block diagram showing one embodiment of the input/output control device. In the figure, the input/output control device U includes a driver circuit, H and rollers, a receiver circuit 27. Ko and 49. It includes latch circuits 30 and 3/, an AND-OR gate 32, an AND gate 33, and monostable circuits 3'l and 3j.

Next, the manual data transfer operation will be described in detail. That is,
Referring to FIG. 3, when the input data payment instruction signal IN and the input data are transferred, the signal AVL indicating that there is sending data in the buffer and data can be supplied on the bus is at logic 1.
/'', and the signal received by the receiver circuit 29, that is, the third control signal appearing on the third signal line B, becomes the logic "O'
At this time, the output of the AND-OR gate 32 becomes logic "/'.

This signal is passed through the latch circuit J/
The latch circuit 3/ outputs data onto the data bus 3 via the driver circuit in response to this Isa signal. At the same time, the output of the AND gate 33 is converted into a signal that becomes logic "L" for a predetermined time by the stability circuit 33, and is sent to the signal line II (first control line) via the driver circuit 26. be done.

After sending this signal, the input/output control device changes the logic state on signal #1ltl to / after sufficient time has elapsed for skew compensation.
” to “o”.

On the other hand, data sent from the input/output control unit f2 via the data bus 3 due to a change in logic "l' to "On" (hereinafter referred to as falling) on the signal line of the channel/bag receiving the signal on the signal aperture. Receive.

This operation is performed when the signal I becomes logic ﾂ/n during input data transfer.
At the time of N and input data transfer, the signal RDY indicating that there is a free space in the data backer /g and that data on the data bus 3 can be received becomes logic "L", and in response to the fall of the signal on the signal line , is realized by the latch circuit 16 latching the data on the data bus 3.

Channel / also changes the signal line 3 to logic "/" in response to the change in signal line da from logic '0' to "/" (hereinafter referred to as rising).
Make it. Similarly, when the signal on the signal line section falls, the signal line j is set to logic "0".

Here, the data buffer control circuit it outputs the number of free spaces in the data buffer, compares this output with the preset output of register J using a comparator 1, and determines that the number of free spaces is greater than the set value. When the signal is low, the signal line 6 (third control line) is set to logic "1" via the driver circuit /'iZ.

Conversely, when the data in the buffer γ of R1 is processed and the comparison result is negative, the signal line 6 becomes logic m-- ON. That is, by sending a warning signal to the input/output control device before an overrun is detected, the input/output control device temporarily suspends the setting of the control signal.

Since the time required for the input/output control device to detect the notice signal varies depending on the distance between the channel and the input/output control device 2, that is, the length of the interface, the value set in the register J depends on the system installation. It is also possible to set an appropriate value in advance before starting data transfer depending on the time or frequency of overrun occurrence during use.

As described in detail, in the present invention, the input/output control device is notified that the remaining data buffer circular data of the channel or the empty area has become smaller than a predetermined value, and the input/output control device By interrupting data transfers when notified.

This has the effect of suppressing the occurrence of unnecessary overruns.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a subsystem to which an embodiment of the present invention is applied, and FIGS. 4 and 3 are block diagrams showing detailed configurations of the channel and input/output control device shown in FIG. 1, respectively. be. //, /ko, core,, J, 2q...receiver%/3.
/lI, /ri. ko, 26...driver, /A, /7.30.3/.
...Latch circuit, -13 circuit...Andor gate, 2
J, 33...Antgeld 1.3J3! ...monostable circuit, 7g...data buffer, /9...data buffer control circuit, 20...comparison count setting register, 2/...comparator, 2da, 36 and 3ri...・Inverter #f Applicant NEC Corporation Representative Patent Attorney Yuta Kumagai 1 Figure 1 Figure 2

Claims (1)

[Claims] In an input/output interface comprising a channel, an input/output control device, first, second, and third control lines for connecting these devices, and a data bus, the input/output control device has a first control line attached to the input/output control device. means for energizing the first control line and deenergizing the first control line after a predetermined period of time has elapsed from the energization; means for suspending until deactivation of a third control line, the channel providing data on the data bus or transmitting data on the data bus in response to detection of activation of the first control line; means for energizing the second control line in conjunction with data capture, and means for energizing the third control line when the number of data that can be supplied or the number of data that can be captured becomes a predetermined value or less; means for energizing the third control line and deenergizing the third control line when the value exceeds the predetermined value;
and means for deactivating the second control line in response to detection of deactivation of the first control line.