DESIGNING SEQUENTIAL

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CHAPTER 7

• DESIGNING SEQUENTIAL
• SYSTEMS

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CE6. A system with one input x and one output z
such that z 1 iff x has been 1 for at least
three consecutive clock times.
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A none, that is, the last input was 0 B one C
two D three or more
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CE7. A system with one input x and one output z
such that z 1 at a clock time iff x is
currently 1 and was also 1 at the previous two
clock times. CE7. A Mealy system with one input
x and one output z such that z 1 iff x has been
1 for three consecutive clock times.
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A none, that is, the last input was 0 B one C
two or more
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Design a Mealy system with one input x and one
output z such that z 1 iff x has been 1 for
exactly three consecutive clock times. A sample
input/output trace for such a system is x 0 1 1
1 1 1 1 1 0 1 1 0 1 1 1 0 1 z 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 1 0 0 0 ?
? A none, that is, the last input was
0 B one 1 in a row C two 1s in a row D three
1s in a row E too many (more than 3) 1s in a
row
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Design a Moore system with one input, x, and one
output z such that z 1 iff x has been 1 for
exactly three consecutive clock times. x 0 1 1 1
1 1 1 1 0 1 1 0 1 1 1 0 1 z 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 1 0 0
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CE8. Design a Moore system whose output is 1 iff
three consecutive 0 inputs occurred more recently
than three consecutive 1 inputs. A sample
input/output trace for such a system is x 1 1 1 0
0 1 0 1 1 1 0 0 1 0 0 0 0 1 1 1 1 0 1 z ? ? ? 0 0
0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0
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CE11. Design a Moore model bus controller that
receives requests on separate lines, R0 to R3,
from four devices desiring to use the bus. It has
four outputs, G0 to G3, only one of which is 1,
indicating which device is granted control of the
bus for that clock period. The low number device
has the highest priority, if more than one device
requests the bus at the same time. We look at
both interrupting controllers (where a high
priority device can preempt the bus) and one
where a device keeps control of the bus once it
gets it until it no longer needs it. The bus
controller has five states A idle, no device
is using the bus B device 0 is using the
bus C device 1 is using the bus D device 2 is
using the bus E device 3 is using the bus
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