The general configuration of the microprogrammed control unit is given below :…
2017
The general configuration of the microprogrammed control unit is given below :
What are blocks B and C in the diagram respectively ?
- A.
Block address register and cache memory
- B.
Control address register and control memory
- C.
Branch register and cache memory
- D.
Control address register and random access memory
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Correct answer: B
Answer: Control address register and control memory.
Explanation: These two blocks implement the fetch stage of the microprogrammed control unit. The control address register holds the address of the microinstruction to fetch, and the control memory (control store) holds the microinstructions themselves.
The Next Address Generator uses external conditions and sequencing logic to produce the address of the next microinstruction.
That address is loaded into the control address register, which provides a stable address to the control memory for the current fetch.
The control memory (control store) is accessed using the address from the control address register and outputs the microinstruction (control signals) and any information needed to form the next address.
Why the other choices are incorrect:
Names like "block address register" or "branch register" do not reflect the standard term for the register used to address microinstructions; the standard term is control address register.
Cache memory and general-purpose random access memory are not the specialized control store used to hold microinstructions. The control memory (control store) is a dedicated storage (often implemented as ROM or writable control store) for microprograms.
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