Table 8-2. Qualifying Symbols for Inputs and Outputs
I
Description
Symbol
4
I
Logic negation at input. External
0
produces internal
1.
Logic negation at output. lnternal
1
produces external
0.
Active-low input.
I
Active-low output.
I
Active-low input in the case of right-to-left signal flow.
I
Active-low output in the case of right-to-left signal flow.
1
Signal flow from right-to-left. If not otherwise indicated, signal flow is from left-to-right.
1
Bidirectional signal flow.
Dynamic input. The transition from the external
0
state to the external
1
state
produces a transitory internal
1
state. At all other times, the internal logic state is 0.
Nonlogic connection.
A
label inside the device symbol will usually define the nature
of the input or output.
I
Analog input or output.
8-57.
Qualifying Symbols for lnternal Connections
8-58.
The internal connections between elements abutted together in a logic symbol are indicated by the sym-
bols shown in
Table 8-3.
Note that the internal (virtual) input is an input originating somewhere else in the
device and is not connected directly to a pin. The internal (virtual) output is likewise not connected to a pin.
Table 8-3. Qualifying Symbols for Internal Connections
I
-
-+-
-
I
lnternal connection.
1
state on left produces
1
state on right.
Symbol
I
'
'6'
'
I
Negated internal connection.
1
state on left produces
0
state on right.
--
--
Description
lnternal input (virtual input). It always stands at its internal
1
state unless affected by
an overriding dependency relationship.
--I--
-
-
-
-
lnternal output (Virtual output). Its affecft on an internal input to which it is con-
nected is indicated by dependency notation.
I
Dynamic internal connection.Transition from
0
to
1
on left produces transitory
1
state on right.
8-59.
Symbols Inside the Outline
8-60.
Table
8-4
shows some of the symbols used inside the outline of a logic symbol. Note particularly that open-
collector, open-emitter, and three-state outputs have distinctive symbols. Also note that an EN (Enable) input af-
fects all the outputs of the circuit and has no affect on inputs. When an Enable input affects only certain outputs
and/or affects one or more inputs, a form of dependency notation will indicate this (refer to paragraph
8-61).
HP
5334B
-
Service Manual
8-10
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