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Cadenti
logic family
medium scale integration
metal oxide semiconductor
ac register
accumulator logic
adder circuit
basic computer design
branch unconditionally
flowchart
input and output communication
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input register
interrupt cycle
logic adder circuits
logic gates
output register
register and memory
binary code
binary number
clock pulse
data types
decimal numbers
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Flip-Flop Input Equations
An example of a sequential circuit is shown in Fig. 1-25. It has one input variable x, one output variable y, and two clocked D flip-flops. The AND gates, OR gates, and inverter form the combinational logic part of the circuit. The interconnections among the gates in the combinational circuit can be specified by a set of Boolean expressions. The part of the combinational circuit that generates the inputs to flip-flops are described by a set of Boolean expressions called flip-flop input equations. We adopt the convention of using the flip-flop input symbol to denote the input equation variable name and a subscript to
The sequential circuit also has an external output, which is a function of the input variable and the state of the flip-flops. This output can be specified algebraically by the expression
y = Ax' + Bx'
From this example we note that a flip-flop input equation is a Boolean expression for a combinational circuit. The subscripted variable is a binary variable name for the output of a combinational circuit. This output is always connected to a flip-flop input.