Browse Prior Art Database

Programmable System Clock Oscillator

IP.com Disclosure Number: IPCOM000089476D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Howe, LD: AUTHOR [+2]

Abstract

During computer system set-ups and field servicing, it is often desirable to run the system at a lower speed to enhance debugging procedures. Furthermore, to change the speed of the system clock oscillator by replacing a board with a slower oscillator card may require the power of the system to be completely shut off, requiring a cold start during the debugging procedure. In addition, future LSI (large-scale integration) computer systems will have oscillator circuitry that can no longer stand alone to occupy an individual card and, accordingly, component replacements would be very hazardous, time consuming and expensive.

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Programmable System Clock Oscillator

During computer system set-ups and field servicing, it is often desirable to run the system at a lower speed to enhance debugging procedures. Furthermore, to change the speed of the system clock oscillator by replacing a board with a slower oscillator card may require the power of the system to be completely shut off, requiring a cold start during the debugging procedure. In addition, future LSI (large-scale integration) computer systems will have oscillator circuitry that can no longer stand alone to occupy an individual card and, accordingly, component replacements would be very hazardous, time consuming and expensive.

It has been found that a multispeed clock oscillator can be provided by having a programmable oscillator where frequency can be easily changed by simply keying in a command or changing a switch or jumper, which could be readily accessible to an engineer or a console operator. Such an oscillator circuit, shown in the figure, utilizes mechanical means to program the oscillator since it is easy and inexpensive to implement. In the figure, JSW controls transistors Q1, Q2 or Q3 to be "on" or "off". By selecting one of the three transistors, there is an appropriate selection of the frequency of oscillation, thereby permitting various system clock speeds. It has also been found that system failures due to timing problems can sometimes be fixed by slowing down the system clock. Using such a programmable clock oscillat...