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24 Datasheet
Electrical Specifications
2.5.2 Overshoot/Undershoot Pulse Duration
Pulse duration describes the total time an overshoot/undershoot event exceeds the
overshoot/undershoot reference voltage (V
CTERM
/GND). The total time could encompass several
oscillations above the reference voltage. Multiple overshoot/undershoot pulses within a single
overshoot/undershoot event may need to be measured to determine the total pulse duration.
Note: Oscillations below the reference voltage cannot be subtracted from the total overshoot/undershoot
pulse duration.
2.5.3 Activity Factor
Activity factor (AF) describes the frequency of overshoot (or undershoot) occurrence relative to a
clock. Since the highest frequency of assertion of any common clock signal is every other clock, an
AF = 1 indicates that the specific overshoot (or undershoot) waveform occurs every other clock
cycle. Thus, an AF = 0.01 indicates that the specific overshoot (or undershoot) waveform occurs
one time in every 200 clock cycles. For source synchronous signals (data, and associated strobes),
the activity factor is in reference to the strobe edge. The highest frequency of assertion of any
source synchronous signal is every active edge of its associated strobe. So, an AF = 1 indicates that
the specific overshoot (or undershoot) waveform occurs every other strobe cycle. The
specifications provided in Table 2-14 through Table 2-21 show the maximum pulse duration
allowed for a given overshoot/undershoot magnitude at a specific activity factor. Each table entry is
independent of all others, meaning that the pulse duration reflects the existence of
overshoot/undershoot events of that magnitude ONLY. A platform with an overshoot/undershoot
that just meets the pulse duration for a specific magnitude where the AF <1, means that there can
be no other overshoot/undershoot events, even of lesser magnitude (if AF = 1, then the event
occurs at all times and no other events can occur).
Figure 2-3. System Bus Signal Waveform Exhibiting Overshoot/Undershoot
000588
V
CTERM
Maximum
Absolute
Ove rshoot
Maximum
Absolute
Undershoot
Time-de
p
endent
Overshoot
Time-de
p
endent
Undershoot
V
REF
V
OL
GND
V
MIN
V
MAX