Intel Embedded Intel486 Hardware Reference Manual page 297

At lower edge rates, the effects of these reflections are not severe. However at higher edge rates,
the rise time of the signal is short with respect to the propagation delay. Thus it can cause prob-
lems as shown in Figure
V
S
Overshoot is caused by poor matching, which occurs when the voltage level exceeds the maxi-
mum (upper) limit of the output voltage. Undershoot occurs when the level exceeds the minimum
(lower) limit. These conditions can cause excess current on the input gates which results in per-
manent damage to the device.
10-9.
Overshoot
Figure 10-9. Overshoot and Undershoot Effects
X
A
Z
S
Figure 10-10. Loaded Transmission Line
PHYSICAL DESIGN AND SYSTEM DEBUGGING
Expected Output Signal
Output Signal Received
Undershoot
.
Z C
0 0
L
Time
A5285-02
B
Z
L
10-13