Hardware Reference
In-Depth Information
Figure 3.27
Exercise 3.7: State Machine Categories
What is the category of the machines in i gures 1.3b, 1.3c, 3.4a, and 3.6a?
Why are the machines of i gures 8.12c and 8.14b said to be of category 2?
Why are the machines of i gures 11.5b and 11.7b said to be of category 3?
Exercise 3.8: State Encoding
List the codewords used to encode the states of the garage door controller of i gure
5.9c in the following cases:
a) With sequential encoding.
b) With Gray encoding.
c) With Johnson encoding.
d) With one-hot encoding.
Exercise 3.9: Number of Flip-Flops
Calculate the number of DFFs needed to encode an FSM with
M
= 8 or
M
= 33 states,
in the following cases:
a) With sequential encoding.
b) With Gray encoding.
c) With Johnson encoding.
d) With one-hot encoding.
Exercise 3.10: Need for Reset #1
Say that the FSM of i gure 5.4b, which implements a basic parity detector, is encoded
using regular sequential encoding (so
pr_state
= '0' in state
zero
and
pr_state
= '1' in
state
one
).
a) Are there any states
outside
the machine (i.e., unused codewords)?
b) Is an explicit reset signal needed when this machine is implemented in an FPGA
(l ip-l ops reset automatically on power-up)? Can deadlock occur in this case?
c) Answer the questions of part b when the l ip-l ops' initial state is arbitrary.
