88e3016 Marvell Semiconductor, Inc., 88e3016 Datasheet - Page 41

• Manufacturer Part Number: 88e3016
• Description: Integrated 10/100 Fast Ethernet Transceiver
• Manufacturer: Marvell Semiconductor, Inc.

Write to register 30 = b'000P PPPP 010N NNNN -- adjusts NMOS strength
Where PPPPP is the 5 bit value for the PMOS strength.
Where NNNNN is the 5 bit value for the NMOS strength.
The value of PPPPP or NNNNN will depend on your board. The ‘11111’ value enables all fingers for maximum
drive strength, for minimum impedance. The ‘00000’ value turns all fingers off for minimum drive strength, for max-
imum impedance. Use a scope to monitor the RX_CLK pin close to the destination. Start with the default auto-cal-
ibrated value and move in each direction to see how it affects signal integrity on your board.
Example: The automatic calibration has a 49 ohm target, but if the trace impedance on board was 60 ohms, you
see reflections from a scope capture taken at the destination. See
that the reflections are eliminated in
Figure 8
NOTE: The trend lines displayed in
Figure 8: PMOS Output Impedance (1.8V, 2.5V) Trend Lines
Copyright © 2006 Marvell
May 4, 2006, Advance
90
80
70
60
50
40
30
20
10
0
and
1
2 3
Figure 9
4
5 6 7
display the trend lines for 1.8V and 2.5V PMOS and NMOS impedance settings.
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Figure 8
Document Classification: Proprietary Information
Figure
PMOS Register Value (Decimal)
and
11.
2.5V
3.3V
CONFIDENTIAL
Figure 9
use nominal values and may vary in production.
Automatic and Manual Impedance Calibration
Figure
10. After manual calibration, you see
Doc. No. MV-S103164-00, Rev. --
Page 41