Question

LITTLE MAN Computing

1. Suppose that the following instructions are found at the given locations in memory: Little Man

40 LDA 60

41 ADD 61

60 724

61 006

a. Show the contents of the IR, the PC, the MAR, the MDR, and A at the conclusion of instruction 40.

b. Show the contents of each register as each step of the fetch-execute cycle is performed for instruction 41.

Answer 1

Answer: Since this is the Little Man Computer Model so the opcode for ADD and LDA instructions are 1 and 5 Respectively.

(a) The Contents of the IR ,The PC, The MAR ,The MDR and A are at the conclusion of instruction 40 are shown below:

IR=560, PC=41,MAR=60, MDR=724

(b) The Contents of each register as each step of the fetch -execute cycle is performed for instruction 41 are as following:

Step 1:

IR=560, PC =41,MAR=41,MDR=161,A=724

Step 2:

IR= 161,PC=42,MAR=41,MDR=161,A=724

Step 3:

IR=161,PC=42,MAR=61,MDR=006,A=724

Step 4:

IR = 161,PC=42,MAR=61,MDR=006, A=730