HP 437B - Page 28

HP 437B
3-STATE
X/Y
X-Y
(Functional
Labels)
MUX
DEMUX
CPU
PIO
SMI
8-10 SERVICE
Table 8-2. Schematic Diagram Notes (5 of 8)
DIGITAL SYMBOLOGY REFERENCE INFORMATION
Input and Output Indicators (Cont'd)
Three-state
Output—Indicates
outputs
that
can
have
a
high
impedance
(dis-
connect)
state
in
addition
to
the
normal
binary
logic
states.
Combinational Logic Symbols and Functions
AND—Al] inputs must be active for the output to be active.
OR—One or more inputs being active will cause the output to be active.
Logic
Threshold—m
or
more
inputs
being
active
will
cause
the
output
to
be
active
(replace
m
with
a
number).
EXCLUSIVE
OR—Output
will
be
active
when
one
(and
only
one)
inputis
active.
m
and
only
m—Output
will
be
active
when
m
(and
only
m)
inputs
are
active
(replace
m
with
a
number).
Logic
Identity—Output
will
be
active
only
when
all
or
none
of
the
inputs
are
active
(i.e.,
when
all
inputs
are
identical,
output
will
be
active).
Amplifier—The
output
will
be
active
only
when
the
input
is
active
(can
be
used
with
polarity
or
logic
indicator
at
input
or
output
to
signify
inversion).
Signal Level Converter—Input level(s) are different than output level(s).
Bilateral Switch—Binary controlled switch which acts as an on/off switch to
analog or binary signals flowing in both directions. Dependency notation should
be used to indicate affecting/affected inputs and outputs. Note: amplifier symbol
(with dependency notation) should be read to indicate unilateral switching.
Coder—Input code (X) is converted to output code (Y) per weighted values or a
table.
The following labels are to be used as necessary to ensure rapid identification of
device function.
Multiplexer—The output is dependent only on the selected input.
Demultiplexer—Only the selected output is a function of the input.
Central Processing Unit
Peripheral Input/Output
Static Memory Interface