Intel® Fast Ethernet Controllers Timing Device (AP-419)
Introduction and Scope
This application note provides information regarding frequency control devices, including crystals and oscillators, for use with all Intel® Ethernet controllers. Several suitable frequency control devices are available; none of which present any unusual challenges in selection. The concepts documented herein are applicable to other data communication circuits, including Physical Layer devices (PHYs).
The Intel® Ethernet controllers contain amplifiers which, when used with the specific external components, form the basis for feedback oscillators. These oscillator circuits, which are both economical and reliable, are described in more detail throughout this document.
The Intel® Ethernet controllers also have bus clock input functionality, however a discussion of this feature is beyond the scope of this document, and will not be addressed.
The chosen frequency control device vendor should be consulted early in the design cycle. Crystal and oscillator manufacturers familiar with networking equipment clock requirements may provide assistance in selecting an optimum, low-cost solution.
The following list of references provide supplemental background material:
• Oscillation Circuit Design Guide Application Note, Epson Electronics America, Inc. (www.eea.epson.com).
• Quartz Crystal Theory of Operation and Design Notes. Fox Electronics (www.foxonline.com).
• Crystal Technical Glossary. Fox Electronics.
• Crystal Frequently Asked Questions. Fox Electronics.
• Resonator Terminology and Formulas. Piezo Technology, Inc. (www.piezotech.com).
• New Crystal Specification for 82541EI/GI and 82547EI/GI, Technical Advisory 162. Intel Corporation.
• Indirect Measurement of Transmitter Reference Frequency, Application Note (AP-457). Intel Corporation.
Read the full Intel® Fast Ethernet Controllers Timing Device Selection Guide Application Note.