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The diagram below shows a high
frequency square wave when observed with an analog scope:
Figure 3: Ringing
Clearly, if this signal were to
be a clock-input to a device, there would be some serious problems. All signals
used as clocks must be verified to see if termination is necessary. Inserting a
resistor on the protoboard between the signal and ground can reduce this swing.
A 100 resistor is ideal for most cases.
Note that with a 100 termination,
the signal's logic high is now about 3.8 Volt, which satisfies the requirements
of a TTL compatible device. If you feel the need to terminate a bus, ask the
front desk for a resistor network. Its logic diagram is as follows:
Figure 4: Resistor Network