US3372378A

US3372378A - Input/output unit switch

Info

Publication number: US3372378A
Application number: US362710A
Authority: US
Inventors: Ernest W Devore; Roy J Smith; John M Tyrrell
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1964-04-27
Filing date: 1964-04-27
Publication date: 1968-03-05
Anticipated expiration: 1985-03-05
Also published as: GB1083171A; NL154342B; CH432067A; DE1574590A1; DE1574590B2; SE329515B; NL6505325A

Description

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I R AR 1 READ BUS P TU-O READ BUS P TC-A Q READ BUS 0 TU 0 READ BUS 2 TC-A READ BUS 2 ru-o READ BUS 5 TU-O READ BUS 5 TC-A E READ BUS 4 TU-O v READ BUS 5 TU-O READ BUS 5 TH RLY READ BUS s TU-O READ BUS 0 TH WRITE ECHO Tu-D WRITE ECHO TC-A READ BUS 7 TU-O A 86 READ BUS P TU-T A L READ BUS D TU-7 READ BUS 1 TC-A RLY READ BUS 1 READ BUS 7 TC-A READ BUS 2 8 READ BUS 5 TU-Y READ BUS 4 TU-Y READ BUS 4 TH READ BUS 5 TU-7 READ BUS 6 TCA RLY WR'TE ECHO READ BUS 6 TU-Y READ BUS 7 TU-Y A7, LO. Q AR United States Patent ()fiice 3 ,372,378 Patented Mar. 5, 1968 3,372,378 INPUT/OUTPUT UNIT SWITCH Ernest W. Devore, Poughlreepsie, Roy J. Smith, Wappingers Falls, and John M. Tyrrell, Hyde Park, N.Y., assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Apr. 27, 1964, Ser. No. 362,710 21 Claims. (Cl. 340-1725) ABSTRACT OF THE DISCLOSURE An input/output (I/O) unit switch operated by a plurality of control units, permitting them to independently select and use any available I/O unit from a plurality of I/O units. No additional computer instruction is needed to recognize the existence of the I/O unit switch, which is a passive device that responds to standard I/O select instructions needed without the I/O switch. Coordinating selection circuitry prevents improper selection of any I/O unit. A modular configuration with nodes having slow speed (relay) bus switching circuits and high speed (semiconductor) control circuits permits full performance in switching and controlling magnetic tape units. The control units may be connected to the same or dilferent computer systems.

This invention relates generally to a switching system for selectively connecting any input/output (I/O) unit of a plurality of I/O units to any control unit of a plurality of control units. All control units can simultaneously operate with different I/O units. Furthermore, any I/O unit can be permanently made not available to any control unit on a selective basis.

The commonest means of selecting an I/O unit from a group of units is via a direct connection between a control unit and each of a plurality of I/O units. In this sense, a control unit is designed to accommodate up toa specific maximum number of I/O units.

Tape units are a form of I/O unit and hereafter are used to represent I/O units generally. Frequently, it is desired to increase the capacity of a magnetic tape unit installation without the use of special apparatus through the use of additional tape controls. In this case, each tape control selects among only its own bank of tape units, and it cannot operate tape units connected to other tape controls.

For example, an overall computer installation may have two tape controls and 16 tape units, in which 8 of the tape units are connected to one control unit while the remaining 8 tape units are connected to the remaining control unit. One tape control can operate only with one of its 8 tape units and cannot operate with the 8 tape units connected to the other control. In this event, the addition of a tape control and its tape units does not increase the flexibility of either the tape controls or the individual tape units, although it increases the I/O capacity of the system due to the addition of more units. It is, therefore, desirable to be able to find a convenient means of increasing the flexibility of an installation so that any of several tape controls can operate with any tape unit among all tape units at an installation. A method of accomplishing this end is a tape unit switch (TUS). The tape unit switch connects between a plurality of the tape controls and a plurality of tape units so that any of the plurality of tape units is selectable by any of a plurality of tape controls.

Various tape unit switches have been suggested, some of which are directly address programmable and require special instructions by the computing system in order to connect a given tape unit to a given tape control. Other tape unit switches are manually controlled to connect a particular tape unit to a particular tape control. The manual switch offers the flexibility of changing a semipermanent tape unit connection, but it cannot provide tape switching between data block transfers by a computer system without first stopping the system, which is highly undesirable.

It is an object of the invention to provide switching means to allow any of a plurality of control units to be connected selectively to any of a plurality of I/O units. In some cases, the total number of available I/O units can exceed the maximum number that can normally be attached to :a control unit.

It is an other object of the invention to provide an I/O switch which can operate without the necessity of any special computer instruction or any other special program intervention by a computing system, and yet can operate under complete computer control.

It is a further object of this invention to provide an I/O unit switch having the general physical configuration of a two-dimensional matrix.

It is another object of this invention to provide a switch that can operate all input-output lines between a control and its selected I/O unit.

It is a further object of this invention to provide switching circuitry that allows an overlapped operation between a high speed tape control unit and a relatively slow I/O unit by overlapping data bus switching with read or write delays of an I/O unit.

It is still another object of this invention to provide means for locking out the availability of a particular I/O unit to any one or more control units.

It is another object of this invention to provide an I/O switch capable of modular expansion for future increase in the number of I/O units and/ or controls in a computer installation.

It is object of this invention to provide an I/O switch between plural I/O units and plural controls, where the controls can be connected to different channels of the same computer system, or to channels of dilferent computer systems, or to channels of a computer system and to oft-line devices.

It is another object of this invention to prevent another control from interfering with the operation of an I/O unit once the I/O unit has been selected by any control.

It is an object of this invention to permit any control to sample the status or type of any I/O unit connected to an I/O switch, even though the I/O unit is being operated by another control.

It is another object of this invention to permit an I/O select instruction from a computer to any of its tape controls to select among any available tape unit in the computer installation.

It is a further object of this invention to provide a plural control-plural tape unit switch capable of switching among its tape units between normal data block transfers to or from a computer with no loss of time in system operation due to switching, compared to the time required to switch between tape units on a single tape control not having a tape unit switch.

The foregoing and other objects, features and advantages of the invention will be apparent from the follow-