Suppose the control memory in fig 72 has 4096 words of 32 bi

Suppose the control memory in fig 7-2 has 4096 words of 32 bits each. The microinstruction has three fields as shown in the diagram. The microoperations field has 12 bits.

a) How many bits are there in the branch address field and the select field?

b) If there are 16 status bits in the system, how many bits of the branch logic are used to select status bit?

c) How many bits are left to select an input for the multiplexer.

Explain each question

218 CHAPTER SEVEN Microprogrammed Control Inst rection code Mapping ogic Stahis Branch logie MUX seleet Multiplexers bits its Subeoutine rezisier SBR) Conuelaldress register CAR) Clock Incrementer Centtol memor Select status bit Micsooperations Branch address Figure 7-2 Selecrion of address for conrrol memoey

Solution

a) 12 bits

b. 12 bits

c. Each multiplexer is a 4x1 multiplexer and 12 multiplexers are needed.