Digital Electronics 1.2 review

Parts of a digital signal

-Amplitude -Time High (tH) -Period (T) - Time Low (tL) -Rising Edge -Falling Edge

555 Timer: Capacitor Charge Cycle

-Capacitor is initially discharged and charges to +12 v (switch A) -Capacitor is initially charged and will discharge to +0 v (switch B)

Increase Charging time by:

-increasing the resistance (lower current= longer charging time) -Increasing capacitance

Sequential Logic

A group of logic elements that contain memory and hence whose value depends on the inputs as well as the current contents of the memory. (Used for finite state machines)

Combinational Logic

A logic system whose blocks do not contain memory and hence compute the same output given the same input.

Binary number

A number composed of just 0s and 1s, also known as a base-2 number.

Digital Signal

A system of discrete states: high or low, on or off, 1 or 0.

decimal number system

A system with 10 numeric values, 0 through 9. (Base 10)

Analog Signal

A type of signal where the data is represented by continuous waves.

Relationship between a capacitor and frequency and duty cycle in a 555 Timer oscillator.

As the capacitor value for C increases, frequency (ƒ) decreases and Duty Cycle (DC) remains constant.

Relationship between a resistor and frequency in a 555 Timer oscillator

As the resistor value for RA increases; frequency (ƒ) decreases and Duty Cycle (DC) increases. As the resistor value for RB increases, frequency (ƒ) decreases and Duty Cycle (DC) decreases.

Calculating the necessary capacitor

C=T/.693(RA+2RB) (Ex: if desired oscillation (Hz) is given, substitute for f, solve for T and continue)

Output is HIGH while the capacitor is:

CHARGING through RA+RB

Output is LOW while the capacitor is:

DISCHARGING through RB

Equations for 555 Timer

F=1/T T=.693 (RA+2RB)C T=0.693(RA+2RB)C

Flip-flop (Frequency and Period)

Frequency and period are inversely related (If period is multiplied by 2, frequency is divided by 2 and vice versa)

NOR logic gate

If input A nor input B are a 1 then output is a 1

hexidecimal number system

Number system that has 16 digits 1 - 9 and A - F. (Base16)

Relationship between a flip-flop added to the design and the effect on frequency

One flip-flop will divide the frequency by 2, two flip-flops will divide the frequency by 4, three flip-flops will divide the frequency by 8, etc... (Divided by two circuit)

NAND logic gate

Output is always 1 unless *both* inputs are 1

Parts of Analog signal

Period, Amp.(peak), Amp.(peak-to-peak)

555 Timer

an 8-pin integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element.

flip-flop circuit

an electrical switch that "remembers" its last position (open or closed) as long as power continuously flows though it

Digital signal standard voltage level

min. value 0V and Max value 5V

Capacitors charge through:

resistors