Question 5) (13 Marks) For the one-bus CPU organization shown in the following c

Question

Question 5) (13 Marks) For the one-bus CPU organization shown in the following complete the given steps (by filling in the blanks) expressed in register transfer notation necessary to execute the following instruction Twos comp Where exc and cyo refer to locations in main memory. This instruction performs MLyl MIxh 1. That is, it loads a value from the following operation, (inverts the bits and then add main memory location x and performs the two's complement may assume that the one), and then stores the result in main memory location y. You ALU is capable of performing the operations F NOT A,F-A+1. The memory locations are assumed to be held in the IR. LO-IR EN-IR LD-Tem EN-0 LD-R0 MEM MAR ADDI ADD ALU SUB EN-1 LD-R1 RESULT BUS EN- RES LO-RES One Bus CPU for question 5, answers will go on following page.

Explanation / Answer

FIRST step isw fetch the instruction

so in( i ) clock 1) BUS and 2) MDR(memory data register)

the reason is because the content of instruction register moves through bus ,then adress of memory is stored in mar ,then write the memory content to Memory adress register

similarly we can fill up the remaining blanks by looking at the diagram

for t(i+1) 1)temp 2)ALU

for t(i+2) 1)PC

for t(i+3) 1)result

for t(i+4) 1)result 2) temp

for t(i+5) 1)mar 2)mdr

for t(i+6) 1)temp 2) result

fo t(i+7) 1)mem(y)

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