Given, say, a 4-bit binary word, every state has a corresponding 2-digit
decimal value. Sadly, not every 2-digit decimal value has a
binary state. The redundant values mean that we wou
If we are going to manufacture a real, physical system which
Boolean function, we should first query the minimum set of physical
We know from a theorem of propositional logic that any truth function
Machine language interpretation
We have established above that the control unit is responsible for
correct sequencing of the control signals which make up the control bus.
In a programmable processor, the correct sequencing is det
It is usually necessary for the processor to be capable of switching between a
number of distinct processes upon receipt of appropriate signals. Each process
generates its own signal demanding attention. These signals are known as
Implementation-Shift register method
An alternative to the above is to adopt the following approach
1. Generate one unique timing signal per required event
2. Use an OR gate to drive each control bit output, thus allowing more than
one signal t
We now turn to the means of representing integers including negative
as well as positive values.
To summarize, data is represented physically as distinct states of
each made up of a collection of bistables. Each possible
An alternative to presenting and manipulating information in textual
form is to use a graphical one. Where information is broken into a
number of classes, such as the values cfw_0,1 of an output variable, a
graphical form is usual
State assignment table
That which seems to add complication, namely the extra
dependence of output upon input as well as state, very often
simplifies design. The cost is that the
Mealy machine is a little less easy to intuitively understand
We begin this section with a brief recapitulation of the nature of a
Moore state machine.
Values output are similarly derived and synchronously communicated.
The property which distinguishes the Moore machine from the Mealy
Memory is equivalent to the concept of a stable physical state. Any
system with only a single stable state will eventually attain that state if
left to itself.
If disturbed, then left alone, it will return to that state. Such a system