Figure 1 shows an ALU with four input register R1, R2, R3 and R4 connected to th

Question

Figure 1 shows an ALU with four input register R1, R2, R3 and R4 connected to the ALU through two multiplexers. All registers can be reset to zero by placing a 1 on the respective CLEAR input, but only registers R1 and R2 can be incremented by placing 1 on the INCREMENT input (CLEAR and INCREMENT inputs are not shown on the diagram below). The select inputs a, b, c and d decides the source operands. L1, L2, L3 and L4 are the load inputs of the registers controlled by 2-bits X and Y which select the destination register. When E = 0, the decoder is disabled (and no register can latch data available on the input bus). The ALU operation table given in table 1. where C1, C2, C3 and C4 are CLEAR inputs of Registers R1, R2, R3 and R4 respectively used to clear the contents of these registers, while 11 and 12 are the increment inputs of R1 and R2 respectively used to increment the contents of these registers. Write the sequence of control words (in hexadecimal) to perform the following operations: R1 leftarrow R4 V 4 R3 leftarrow R2 - R1 if C = 1, R1 leftarrow 1

Explanation / Answer

Answer:

The micro operations are add,sub,jmp and beq followed by control words of 1100,1101,1001 and 1000.Next the hexadecimal notation is given as 0x10,0x11,0x01 and 0x00.

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