82551IT Datasheet, PDF (87/102 Pages) Intel Corporation – Fast Ethernet PCI Controller

Networking Silicon — 82551IT
11.4
Timing Specifications
11.4.1
Clocks Specifications
11.4.1.1 PCI Clock Specifications
The 82551IT uses the PCI Clock signal directly. Figure 20 shows the clock waveform and required
measurement points for the PCI Clock signal. Table 55 summarizes the PCI Clock specifications.
Figure 20. PCI Clock Waveform
0.475V_CC
0.4V_CC
0.325V _CC
0.6V_CC
T_high
T_cyc
0.2V_CC
T_low
0.4V_CC p-to-p
(minimum)
Table 55. PCI Clock Specifications
Symbol
T1 T_cyc
T2 T_high
T3 T_low
T4 T_slew
Parameter
CLK Cycle Time
CLK High Time
CLK Low Time
CLK Slew Rate
Min
Max
Units Notes
30
ns
1
11
ns
11
ns
1
4
V/ns
2
NOTES:
1. The 82551IT will work with any PCI clock frequency up to 33 MHz.
2. Rise and fall times are specified in terms of the edge rate measured in V/ns. This slew rate is met across the
minimum peak-to-peak portion of the clock waveform as shown in Figure 20.
11.4.1.2 X1 Specifications
X1 serves as a signal input from an external crystal or oscillator. Table 56 defines the 82551IT
requirements from this signal.
Table 56. X1 Clock Specifications
Symbol
T8 Tx1_dc
T9 Tx1_pr
Parameter
X1 Duty Cycle
X1 Period
Min
40%
Typical
40
Max
60%
Units Notes
ns ±30 ppm
Datasheet
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