Timing
CSU22022, 10th Lecture, Dr. M. Manzke, Page: 1
Control Unit Design
Two contrasting approaches to control unit design have evolved:
Hard-wired Micro-coded
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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=AB
Product = Multiplier Multiplicand
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Bit Products
We can generate the bit products:
Pi i=0, n-1 0 if ai=0 Pi=aiB= =ai B
Bifai=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
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Binary Multiplier ASM
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