Hi,
According to AP-419, Revision 1.2, September 2004, Section 3.3 interprets the IEEE 802.3 Frequency Tolerance as +/-50ppm, "referenced to a standard temperature of 25° C".
Should I interpret this as +/-50ppm @25° C, with a wider tolerance for temperature, built into the IEEE 802.3?
While I've been able to correlate that the IEEE 802.3 Frequency Tolerance is given as +/-50ppm, for 100Base-TX, I've not been able to correlate whether it is referenced to a standard temperature of 25° C, or whether that represents the total ppm budget including Nominal Frequency Tolerance, Over Temperature and Ageing factors. The latter seems more appropriate for such a timing specification, because the accuracy will be required for whatever temperature range and lifetime the network components are required to operate in.
Clarification of what revision of 802.3 the AP-419 might align to might help me understand this. If anyone can assist, I'd appreciate it.
Thanks,
Andy Jones