ENGINEERING LOGIC DIAGRAMS
Engineering Logic Diagrams Summary
This chapter reviewed the seven basic symbols used on logic diagrams and the
symbols used for six of the more complex logic devices.
There are three types of time delay devices:
Type One - delays the output signal for a specified period of time
Type Two - only generates an output for the specified period of time
Type Three - receipt of an input signal triggers the device to output a
signal for the specified time, regardless of the duration of the input
This device, although occasionally used on component and system type logic diagrams,
is principally used in solid state logic diagrams (computers).
Binary counter - Several types of binary counters exist, all of which are constructed of
flip-flops. The purpose of a counter is to allow a computer to count higher than 1,
which is the highest number a single flip-flop can represent. By ganging flip-flops,
higher binary numbers can be constructed. Figure 10 illustrates a common symbol used
for a binary counter.
Shift register - Is a storage device constructed of flip-flops that is used in computers to
provide temporary storage of a binary word. Figure 10 shows the common symbol used
for a shift register.
Half adder - Is a logic circuit that is used in computer circuits to allow the computer to
"carry" numbers when it is performing mathematical operations (for example to perform
the addition of 9 + 2, a single 10s unit must be "carried" from the ones column to the
tens column). Figure 10 illustrates the symbol used for a half adder.
The important information in this chapter is summarized below.