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Authored by: Anonymous on Tuesday, May 15 2012 @ 06:30 AM EDT |
You're confusing symbolic references with logical representations, and they're
not the same thing.
1 and 0 are logical representations for voltage levels of +5V and 0V in some
digital semiconductor systems, but they're not symbolic references because no
symbol resolution is performed.
If you labelled two parts of a digital circuit as A and B, and using a lookup
mechanism of some kind (say a probe on a logic analyser) you discovered that A
currently had a value of logic 1 and B had a value of logic 0, then A and B are
being used as symbols in your circuit, and you had to employ some kind of symbol
resolution mechanism to determine their current values. The key to
understanding this is to note that nothing in the symbol A or in the symbol B
tells you anything about the value associated with each symbol in the circuit
--- A and B are purely symbolic, and their values cannot be determined from
inspection of their names.
Note that in addition to 1 and 0 being logical representations of voltage levels
in the above example, in a logic circuit they can also be numerical references.
The simplest illustration of this is a logic value of either 1 or 0 used as the
1-bit address of a 2-word memory. Its value can only be 1 or 0, and which of
these two values it is can be determined by direct inspection, so it's a numeric
reference. There is no need to look up its value using any additional mechanism
because its value is encoded in the 1 or 0 numeric reference itself. 1 and 0
are not symbolic references since they can only have a value of 1 and 0
respectively, and nothing else, so there is no symbol to resolve.[ Reply to This | Parent | # ]
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- Disagree - Authored by: Ian Al on Tuesday, May 15 2012 @ 07:01 AM EDT
- Disagree - Authored by: Anonymous on Tuesday, May 15 2012 @ 11:24 AM EDT
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