A memory unit has a capacity of 65,536 words of 25 bits each. It is used in conjunction with a generalpurpose computer. The instruction code is divided into four parts: an indirect mode bit, operation code, two bits that specify a processor register (General purpose register), and an address part.
Q(1) A memory unit has a capacity of 65,536 words of 25 bits each. It is used in conjunction with a generalpurpose computer. The instruction code is divided into four parts: an indirect mode bit, operation code, two bits
that specify a processor register (General purpose register), and an address part.
a) What is the maximum number of operations that can be incorporated in the computer if an instruction is
stored in one memory word?
b) Draw the instruction word format indicating the number of bits and the function of each part.
c) How many processor registers are there in the computer and how many bits in each?
Q(2) A computer is available without an instruction pointer (IP) or program counter (PC). Instead, all
instructions contain three parts: an operation code, an address of an operand, and the address of the next
instruction. The operation code consists of 6 bits and the computer has a memory unit of 8192 words.
a) How many bits must be in a memory word if an instruction is stored in one word? Show the instruction word
format.
b) What other register is needed in the control unit besides an operation register?
c) List the micro-operations for the instruction fetch cycle of this computer. Use any register specified in part (b).
Q(3) An instruction in address (021)16 in the simple machine has a mode bit I = 0, an operation code of the
AND instruction, and an address part equal to (083)16. The memory word at address (083)16 contains the
operand (B8F2)16 and the content of the AC is (A937)16. Go over the fetch and execute cycles and determine the
content of the following registers at the end of the execute cycle: PC, MAR, MBR, AC, and OPR. Repeat the
problem six more times starting with the operation code of another memory reference instruction with the initial
values as defined earlier.
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