Indirect Probing Setup - Intel 82541PI Design Manual

82541PI(ER) and 82562GZ(GX) Dual Footprint LOM Design Guide
A.3 Indirect Probing Method
The indirect probing test method is applicable foremost devices that support 100BASE-T. Since
probe capacitance can load the reference crystal and affect the measured frequency, the preferred
method is to use the indirect probing test method when possible.
Almost all Intel Ethernet controllers that support 1000BASE-T Ethernet can provide a buffered 125
MHz clock, which can be used for indirect probing of the transmitter reference clock. The buffered
125 MHz clock will be a 5X multiple of the crystal circuit's reference frequency
Different LAN devices may require different register settings, to enable the buffered 125 MHz
reference frequency. Please obtain the settings or instructions that are appropriate for the LAN
controller you are using.
LAN Silicon IEEE Test Out +
LAN Silicon IEEE Test Out -
Figure 19. Indirect Probing Setup
70
P6246 or similar
2-pin
high impedance
header
probe
with less than 1 pF
50 ohm Coaxial
Cable
(Figure
input
Ch.1
Tektronix
input
Ch.2 Power Supply
50 ohm
125.00047
input
Tektronix CMC251
or a similar capability
Frequency Counter
Application Note (AP-468)
19).
1103
Probe