8. A two-word instruction is stored at location 200 with its address field at lo

Question

8. A two-word instruction is stored at location 200 with its address field at location 201 (all numbers in hexadecimal). The first word of the instruction specifies the operation code and mode; the second word specifies the address part.

The values of the program counter (PC register), a general register (R1), the index register (XR), the base register (BR), and certain addresses in memory are as shown below.

Evaluate the effective address and the value that is loaded into the AC if the addressing mode of the instruction is:

Addressing Mode

Effective address

Value of the operand loaded into the AC

a)

Immediate

b)

Direct addressing

c)

Indirect addressing

d)

Register

e)

Register indirect

f)

Relative address

g)

Base register addressing

h)

Indexed addressing

Addressing Mode

Effective address

Value of the operand loaded into the AC

a)

Immediate

b)

Direct addressing

c)

Indirect addressing

d)

Register

e)

Register indirect

f)

Relative address

g)

Base register addressing

h)

Indexed addressing

Explanation / Answer

Addressing Mode |||| Effective address |||| Value of the operand loaded into the AC a) Immediate |||| 201 |||| 400 b) Direct addressing |||| 400 |||| 300 c) Indirect addressing |||| 300 |||| 600 d) Register |||| R1 |||| 900 e) Register indirect |||| 900 |||| 850 f) Relative address |||| 602 |||| 802 g) Base register addressing |||| 600 |||| 800 h) Indexed addressing |||| 700 |||| 500

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