The following table shows part of the instruction set for a processor. The processor has two registers: the Accumulator (ACC) and an Index Register (IX).

Instruction set

opcode	operand	explanation
LDM	#n	Immediate addressing. Load the number n to ACC
LDD		Direct addressing. Load the contents of the location at the given address to ACC
INC		Add 1 to the contents of the register (ACC or IX)
STO		Store the contents of ACC at the given address
ADD	#n / Bn / &n	Add the number n to the ACC
ADD		Add the contents of the given address to the ACC
DEC		Subtract 1 from the contents of the register (ACC or IX)
END		Return control to the operating system

can be an absolute or symbolic address. # denotes a denary number, e.g. #123. B denotes a binary number, e.g. B01001010. & denotes a hexadecimal number, e.g. &4A.

The current contents of memory are:

Memory contents

address	data
100	200
101	205
102	100
103	50
…
200	101
201	100
202	20
203	13
204	220
205	30

Complete the table to identify the data that will be stored in the accumulator after each set of instructions has been executed.

accumulator current data	set of instructions	new accumulator data
B11001010	ADD B00000010 INC ACC	Table answer row1_new accumulator data
#100	LDM #200 ADD 200	Table answer row2_new accumulator data
#103	LDD 103 DEC ACC DEC ACC	Table answer row3_new accumulator data

3(b)(i)Bit ManipulationMedium2 marks

The instruction set also contains the following instructions:

Bit manipulation instructions

opcode	operand	explanation
AND	#n / Bn / &n	Bitwise AND operation of the contents of ACC with the operand
AND		Bitwise AND operation of the contents of ACC with the contents of
XOR	#n / Bn / &n	Bitwise XOR operation of the contents of ACC with the operand
XOR		Bitwise XOR operation of the contents of ACC with the contents of
OR	#n / Bn / &n	Bitwise OR operation of the contents of ACC with the operand
OR		Bitwise OR operation of the contents of ACC with the contents of
LSL	#n	Bits in ACC are shifted logically n places to the left. Zeros are introduced on the right hand end
LSR	#n	Bits in ACC are shifted logically n places to the right. Zeros are introduced on the left hand end
CSL	#n	Bits in ACC are shifted n places to the left using a cyclic shift
CSR	#n	Bits in ACC are shifted n places to the right using a cyclic shift
ASL	#n	Bits in ACC are shifted n places to the left using an arithmetic shift
ASR	#n	Bits in ACC are shifted n places to the right using an arithmetic shift

can be an absolute or symbolic address. # denotes a denary number, e.g. #123. B denotes a binary number, e.g. B01001010. & denotes a hexadecimal number, e.g. &4A.

Write the bit manipulation instruction that will set the ACC to &0.

Answer

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3(b)(ii)Bit ManipulationEasy1 mark

The ACC currently contains the following binary value: 0 0 1 1 0 1 0 1

Write the result after the instruction LSR #3 is run.

Answer

3(c)Assembly Language Addressing ModesMedium3 marks

Immediate, relative and direct are three modes of addressing used in assembly language programming.

Identify and describe one additional mode of addressing used in assembly language programming. Include an example of an instruction that uses your selected mode of addressing in your answer.

Mode of addressing

Description with example

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