1. State Machine Realizations
9/26/2008
ECE Lecture 6

2. Another type of system
One Hot encoding – only one of the state flip-flops is ever a 1. All the other state flip-flops are a 0.
Requires n flip-flops for an n state machine.
Ideal for a state machine having a set of 1-out-of-s coded outputs indicating the current state
9/26/2008
ECE Lecture 6

3. A D-to-A Converter Design a successive approximation A-to-D converter
Will do a 10 bit conversion
Another designer is responsible for the design of the analog comparator
A different designer is responsible for the D-to-A converter within the unit
Your job is to design the digital control circuitry
9/26/2008
ECE Lecture 6

4. The system
The D-to-A system
9/26/2008
ECE Lecture 6

5. The States
The states are fairly simple
9/26/2008
ECE Lecture 6

6. One Hot Encoding
There are 10 distinct state during conversion – each state represents which bit is being converted
Also an initial state and the conversion complete state
The architecture lends itself to one-hot encoding of the states
9/26/2008
ECE Lecture 6

7. Why One hot encoding
One hot encoding typically leads to minimal excitation equations
Minimal excitation equations = lower complexity logic
Lend itself to bit slice logic
9/26/2008
ECE Lecture 6

8. Bit slice logic
Bit slice logic – the same logic is used for each slice. There may be minor modifications needed for the end slice.
Excellent for VLSI implementations
9/26/2008
ECE Lecture 6

9. The slice here Slice is simply repeated for the number of bits.
9/26/2008
ECE Lecture 6