week 6 Flashcards
What is a sequential logic circuit
and what signals is it dependant on
circuit generates output signals with a feedback path
dependant on both input and output signals
what 2 ways is a digital logic circuit classified
combinational or sequential
what is a combinational logic circuit
and what signal is dependant
collection of 7 basic logic gates which generates 1 or more output signals
dependant on input signal
what further 2 ways can a sequential logic be further divided into?
synchronous and asynchronous
what do synchronous logic systems have
2
a common clock signal to all memory elements
fixed frequency for outputs
what do asynchronous logic systems have
don’t require any clock signals
feedback the current output state back to the inputs
very fast response time
what is a ‘flip flops’ in sequential logic devices
building blocks in the system
only have 1 function
they only store “1” or “0”
in which applications can a “flip flop” enable binary counters
- analogue to digital converters
- frequency division for accurate digital clocks
- serial to parallel and parallel to serial conversion of data
- frequency meters, RPM/speed measurement
what is the most basic type of a “flip flop”
Set-Reset input
how does the Set-Reset input function (flip flop)
if SET INPUT is held high then contents of FF will be 1 after application of clock pulse
what device is the easiest for storing single binary digit
D-type flip-flop is the easiest device
what is a D-type flip-flop
A D-type flip-flop is a clocked flip-flop which has two stable states. A D-type flip-flop operates with a delay in input by one clock cycle. Thus being called many D-type flip-flops
what is a J-K flip flop
a gated SR flip-flop with the addition of a clock input circuitry that prevents the illegal or invalid output condition that can occur when both inputs S and R are equal to logic level “1”.
what do manufacturers of flip flops chips provide
additional inputs called “preset” and “clear” function
what is the use for “preset” and “clear”
they enable the user of a complex logic circuit to initialise or set up a known starting condition prior to the operating system
