Browse Prior Art Database

Operation Monitoring

IP.com Disclosure Number: IPCOM000075414D
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Edstrom, GH: AUTHOR [+4]

Abstract

In data processing systems, an unusual operational condition in the peripheral subsystem is indicated by an I/O controller supplying a DEVICE END signal contemporaneously with the UNIT CHECK signal to the CPU. The DEVICE END indicates that an operation by a peripheral device associated with the I/O controller has ended its operation; and UNIT CHECK indicates that the operation end is abnormal, requiring special attention.

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Operation Monitoring

In data processing systems, an unusual operational condition in the peripheral subsystem is indicated by an I/O controller supplying a DEVICE END signal contemporaneously with the UNIT CHECK signal to the CPU. The DEVICE END indicates that an operation by a peripheral device associated with the I/O controller has ended its operation; and UNIT CHECK indicates that the operation end is abnormal, requiring special attention.

In magnetic tape subsystems, magnetic tape units (MTU's) perform free- standing operations such as rewind, wherein the tape is moved until load point is positioned adjacent a sensing transducer. If, during this free-standing operation, the peripheral device or MTU was manually reset, dropped READY or power went off and the like, the CPU must learn of it via the I/O controller or by manual intervention.

When initiating the free-standing operation, the I/O controller, which may be microprogrammed, makes an internal electrical notation that the device is committed to the I/O controller and that a DEVICE END is pending. The I/O controller repeatedly senses status signals on two lines from MTU which, respectively, indicate that MTU is BUSY or NOT BUSY, or an INTERRUPT or NO INTERRUPT is being supplied. During such free-standing operation, a BUSY signal must be supplied. The I/O controller responds in a change in the BUSY to NOT BUSY line, even though there is no change on the INTERRUPT line to examine the device pending status st...