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An Apparatus Monitors And Reports Frequency Of Multiple Clocks

IP.com Disclosure Number: IPCOM000020331D
Original Publication Date: 2003-Nov-13
Included in the Prior Art Database: 2003-Nov-13
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Abstract

A chip is described that monitors and reports the status of system oscillators.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 89% of the total text.

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An Apparatus Monitors And Reports Frequency Of Multiple Clocks

Oscillators in electronic equipment are extremely important but it is difficult to automatically determine if a given oscillator is running. It is even more difficult to determine an oscillator's frequency.

A new chip that serves as a "Clock Monitor" is invented and diagrammed below. The chip is commanded, through its serial interface, to select, from its input, a given clock (oscillator). The microcontroller in the chip uses the chip's input multiplexer to select the desired clock.

Low Frequency Clock Measurement

A low frequency clock rate is determined by measuring its period. One method for performing this is to take the difference between microcontroller timer values at two rising edges of the clock. This is the period of the clock and the inverse is the clock's frequency.

High Frequency Clock Measurement A high frequency clock is measured by counting clocks for a predefined period such as a millisecond and then multiplying the resulting count appropriately (one thousand, in this case). If necessary, a prescaler can be used to successively divide a high frequency clock's rate by two until an appropriate frequency is established for counting.

The measurement is reported back on the serial interface. A period of zero indicates a nonfunctioning oscillator. Now, the numerous clocks in a system can each be routed to one more location - the new Clock Monitor chip - and their status can be continually mo...