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FORDHAM UNIVERSITY CSLU 3593
Fordham College Lincoln Center Computer Organization
Dept. of Computer and Info. Science Spring, 2005
Homework Assignment 3
Due date: February 14
-  §§B.2,B.3 A combinational circuit
is to be designed that compares two 2-bit (unsigned) binary numbers
and . Thus it has 4 inputs, 2 for and 2 for .
It has 3 outputs, , , and : is true if , is
true if , and is true if numerically. Write down the
truth table for this circuit, and express each output as a sum of
minterms (using notation).
-  §§B.3 A combinational circuit is to
be designed for a quality-control station on an assembly line. The
circuit has three inputs, , , and providing the results of
quality checks, and one output that is true if the product
passes the test. If is false, then the product fails regardless
of and . If is true, then the product passes if either
or is true. It is not possible for both and to be
true at the same time. Write down the function table for this
circuit, showing both input and output don't-cares. Write down a
boolean expression for in sum-of-products form, using the
don't-cares to make as simple as possible.
-  §B.8 A T (or toggle)
flip-flop has a single control input besides the clock. If
, then the flip-flop holds its output steady. If ,
then upon arrival of the clock signal, the flip-flop changes its
output to the complement of what it was before. Show how to
implement a T flip-flop using an edge-triggered R-S flip-flop and
some external logic gates.
-  §B.8 Figures B.8.8 and B.8.9 on
pages B-55 and B-66 illustrate the implementation of the register
file for the MIPS datapath. Pretend that a new register file is to
be built, but that there are only two registers, one read port and
one write port, and that each register has only 2 bits of data.
Draw a new figure combining the designs in Figures B.8.8 and B.8.9
into one figure with both write port and read port implementations
shown, and in which every wire corresponds to only 1 bit of data
(unlike the figures in the text, in which some wires are 1 bit, some
are 5 bits, and some 32 bits). Depict the registers as D
flip-flops. You do not need to show how to implement a D flip-flop,
a decoder, or a multiplexor.