HP 5004A, Руководство по эксплуатации и обслуживанию

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M o d e l
Service
NEGATIVE
Alternatively, by assigning the relationship L=l at both input and output, Device can
perform the OR function and Device can perform the AND function. Such
a
consistent
assignment
i s
referred to as negative logic. The corresponding logic symbols would be:
DEVICE DEVICE
8-22. MIXED LOGIC. The use of the polarity indicator symbol automatically invokes a
mixed-logic convention. This is, positive logic is used at t h e i n p u t and outputs that d o n o t have
polarity indicators, negative logic
i s used at the inputs and outputs that have polarity indicators.
EXAMPLE 6 EXAMPLE
7
FUNCTION T A B L E FUNCTION TABLE
H
L
This may be shown either of two ways: This may be shown either of two ways:
Note the equivalence of these symbols to ex-
Note the equivalence of these symbols to ex-
amples and
2
and the fact that the function amples
3
and and the fact that the funcion
table
is a
positive-logic translation
L=O table
i s
a positive-logic translation
of the NAND truth table, and also note that the of the NOR truth table, and note that the
function table
i s
the negative-logic translation
function table
is
the negative-logic translation
of the NOR truth table, given in
of the NAND truth table, given in
Example
3.
Example 1 .
8-23.
It
should b e noted that can easily convert f r o m thesymbology of positive-logic merely
b y substituting a polarity indicator for each negative indicator while leaving the
distinctive shapes alone. T o convert f r o m t h e symbology of negative logic, a polarity indicator
is substituted for each negation indicator (
o )
and the
OR
shape i s substituted for t h e A N D
shape o r vice versa.
8-24. It was shown that any device that can p e r f o r m
OR
logic can also perform
AND
and vice versa. D e Morgan's transformation i s illustrated in Examples 1 through
7.
The rules o f
the transformation are:
1. A t each input o r output having a negation o r polarity indicator, delete t h e
indicator.
2. A t each i n p u t or output n o t having an indicator, add a negation o r polarity
indicator.
3. Substitute t h e A N D symbol for t h e
OR
symbol o r vice versa.
These steps d o n o t alter the assumed convention; positive-logic stays positive,
logic stays negative, and mixed-logic stays mixed.
L L H