Waveform 1.1 Basic Digital Waveform Parameters 1 Paul Godin Updated September 2007 Last edit Sept 2009

Waveform 1.2 Digital Waveform Logic 1 Logic 0 Ideal Waveform

Waveform 1.3 Waveform Parameters ◊Periodic: A waveform that recurs at regular intervals, that has repeating cycles. ◊Aperiodic: A waveform that is irregular, that has timing cycles that vary. Periodic Aperiodic Name examples of periodic and aperiodic waveforms

Waveform 1.4 Time Period: Time for one complete cycle. Symbol: T Units: seconds T 1 Cycle

Waveform 1.5 Time Frequency (f) = 1/ T T Frequency applies to periodic signals

Waveform 1.6 Time Time High (t H ) and Time Low (t L ) tHtH tLtL T

Waveform 1.7 Duty Cycle Duty cycle describes the ratio of the time in the high state versus the overall period of the pulse. Typically expressed in percent. T tHtH tLtL What is the approximate Duty Cycle of this waveform?

Waveform 1.8 Exercise 1 What is the approximate duty cycle of the following waveforms?

Waveform 1.9 Exercise 2 ◊What is the pulse width of a signal, given: ◊T = 2 seconds ◊DC = 50% ◊What is the pulse width of a signal, given: ◊T = 4 seconds ◊DC = 75% ◊What is the duty cycle of a signal, given: ◊T = 2 seconds ◊Pw (pulse width) = 0.5 seconds

Waveform 1.10 Voltage ◊The TTL devices used in this course are based on 5 Volt / 0 Volt logic. ◊Other devices may function on different values. Many portable digital devices function on 3 Volts

Waveform 1.11 Typical Waveform ◊Due to the effects of Inductance, Capacitance, noise, grounding, device properties and other factors, digital signals tend to be electrically less than perfect. These negative effects usually increase with frequency. Typical Waveform Over-shoot Pre-shoot Ringing Rise time Fall time Droop

Waveform 1.12 Logic Values TTL Voltage – Input logic values 5 V 2.0 V 0.8 V 0 V Logic Low Logic High Undefined

Waveform 1.13 Logic Values with Typical Waveform 5 V 2.0 V 0.8 V 0 V Logic Low Logic High Undefined

Waveform 1.14 End gmail.com