HP 5004A, Operating And Service Manual

Page: 50 / 74

Model
Service
8-25. The choice of symbol may be influenced by these considerations: being
performed may best be understood as
A N D or OR. (2) In a function more complex than a basic
gate, the inputs will usually be considered as inherently active high or active low the and
inputs of a flip-flop are active high and active low, respectively).
(3)
In a chain of logic,
understanding and the writing of logic equations are often facilitated if active-low or negated
outputs feed into active-low or negated inputs.
8-26. Other Symbols
8-27. M o r e symbols are required to depict complex logic diagrams. Some of the other symbols
are as follows:
Dynamic input activated by transition from a low level to a high level. The
opposite transition has no effect at the output.
Dynamic input activated by transition from a high level to a low level. The
opposite transition has no effect at the output.
Exclusive OR function. 'the output will assume its indicated active level if and
only if one and only one of the two inputs assumes its indicated active level.
Inverting function. The output is low if the input
i s
high and it i s high if the input
is low. The two symbols shown are equivalent.
Noninverting function. The output
is
high if the input i s high and it is low if the
input i s low. The two symbols shown are equivalent.
OUTPUT DELAY. The output signal is effective when the input signal returns
to its opposite state.
EXTENDER. Indicates when a logic function increases (extends) the number
of inputs to another logic function.
FLIP-FLOP. A binary sequential element with two stable states: a set (1) state
and
a
reset state. Outputs are shown in the state when the flip-flop
i s
set.
I n the reset state the outputs will be opposite to the set state.
RESET. A 1 input will reset the flip-flop. A return to will cause no further
effect.
SET. A 1 input will set the flip-flop. A return to will cause no further action.
TOGGLE. A 1 input will cause the flip-flop to change state. A return to will
cause no further action.