CSU22022, 10th Lecture, Dr. M. Manzke, Page: 1
Timing
CSU22022, 10th Lecture, Dr. M. Manzke, Page: 2
Control Unit Design
Two contrasting approaches to
control unit design have evolved:
Hard-wired
Micro-coded
CSU22022, 10th Lecture, Dr. M. Manzke, Page: 3
Example
We will consider a shift-and-add multiply circuit
as an example of each design approach.
If A and B are n-bit unsigned integers.
To compute their product P:
P = A B
Product = Multiplier Multiplicand
CSU22022, 10th Lecture, Dr. M. Manzke, Page: 4
Bit Products
We can generate the bit products:
Pi i=0, n-1
0 if ai=0
Pi = aiB = = ai B
B if ai=1
j
PPj = Pi2i = Pj2j + PPj-1
i=0
P = PPn-1
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Hand Multiplication
P0
P121
P222
P323
P424
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Hardware Multiplication
a. Overflow temporarily occurred
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Binary Multiplier Diagram
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Binary Multiplier
The figure on the previous slide shows:
Datapath
Status signals Z and Q0
External Input
G = Go
Output
CSU22022, 10th Lecture, Dr. M. Manzke, Page: 9
Binary Multiplier ASM