Browse Prior Art Database

Device Service System

IP.com Disclosure Number: IPCOM000074031D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Dix, GL: AUTHOR

Abstract

Devices 1 through N are serviced by control unit 10 in a manner that each device has the same maximum wait for service. Each device has a Service-Required conductor 15 which is energized by the device whenever service is required. Control unit 10 includes continuously running oscillator 20 which advances address counter 21 via AND circuit 22.

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Device Service System

Devices 1 through N are serviced by control unit 10 in a manner that each device has the same maximum wait for service. Each device has a Service- Required conductor 15 which is energized by the device whenever service is required. Control unit 10 includes continuously running oscillator 20 which advances address counter 21 via AND circuit 22.

If a device energizes its service-required line 15 and its associated Address- Out line 17 is raised by counter 21, AND circuit 16 passes a Service-In signal to set flip-flop 23 via OR circuit 24 and AND circuit 25. This action inhibits the advancement of address counter 21 until servicing of the device is completed.

The Service-Out signal from 23 acknowledges service to the device and also activates I/O control logic 26. I/O control logic 26 includes timing circuits which generate an End Service signal for resetting 23. This allows address counter 21 to advance and thereby address another device. Of course, if a device does not require service, the service-in line is not raised and counter 21 continues to advance.

In this example, each device is serviced for the same length of time. An alternate arrangement would be to service the devices for variable lengths of time. This would be accomplished by having each device provide a signal to the I/O control logic 26. The end service signal would be generated whenever a device indicated that it no longer required service.

The Other I/O lines connected betwee...