Browse Prior Art Database

EMC TEST MODE FOR DIGITAL IC'S

IP.com Disclosure Number: IPCOM000009564D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Sep-03
Document File: 1 page(s) / 45K

Publishing Venue

Motorola

Related People

Chris Dewitt: AUTHOR

Abstract

The use of high speed embedded CPUs and other digital IC's with oscillator's in products causes radiated and conducted emissions of RF energy. Because these parts have many signal lines and the coupling of unwanted signals to the outside world is often complex it is often difficult to determine which of these signals causes a specific emission.

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Developments Technical 0 M MO7-OROLA

EMC TEST MODE FOR DIGITAL IC'S

by Chris Dewitt

  The use of high speed embedded CPUs and other digital IC's with oscillator's in products causes radiated and conducted emissions of RF energy. Because these parts have many signal lines and the coupling of unwanted signals to the outside world is often complex it is often difficult to determine which of these signals causes a specific emission.

  A digital IC could be equipped with a means of putting the part into an EMC diagnostic mode that allows the pins of the part to toggle at the clock rate. In addition a mask register could be implemented to select which pins are allowed to toggle. This mask could be for instance a small register indicating a

single pin number to toggle or a larger register hav- ing a bit per pin enabling any combination of pins to toggle. The part could be pm into the test mode and have its mask register set by simple embedded code, a development tool such as an emulator or back- ground mode interface or via boundary scan tech- niques. The effect of these signals could then be observed using whole product testing methods that include the enclosure, any interconnecting cables and loads. Testing can then be done in an emissions test chamber or using current probes on the cables. This is preferable to probing the PC board since it includes the effect of all coupling mechanisms in the product.

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