Question

LOAD-STORE PROGRAM EXAMPLE Write an Assembly program to add two 8-bit numbers. C A+B lds r16, A lds rl7, B : 1. Load variables add E16, :172 Do something 2. Do something sts C, r16 : 3. Store answer Identify the operation, source operand, destination operand in the first Data Transfer insiruction. Identify the source/destination operand in the Arithmetic and Logic (ALU) instruction. .What addressing mode is used by the source operand, in the first instruction? Show contents of Flash Program Memory (mnemonics) Show contents of SRAM Data Memory, assuming variables are stored in sequential memory locations starting at address 010016 Modify the program to leave register r16 unchanged by making a copy (use r15).

Please answer the list questions above with explanation. Thank you

Answer 1

1) First data transfer instruction is load instruction on line 1.

It has a syntax load destination, source.

For the given instruction lds r16,A,

source operand is A

destination operand is r16

operation is load operation

2)The arithmetic and logical instruction is add operation.

It has a syntax add destination, source.

add r16,r17

source operand is r17

destination operand is r16

operation is add operation : r17 to r16 and store in r16

3) In the first instruction, load uses direct addressing mode to load contents of A in register r16.

4)mnemonic is short 3 alphabet term used for instructions to denote a particular instruction

Operation	Mnemonic	Source Operand	Destination Operand	Description
Load	LDS	A	r16	loads contents of A to r16
Load	LDS	B	r17	loads contents of B to r17
Add	ADD	r17	r16	r16 = r16 + r17
Store	sts	r16	C	Stores value in register r16 to C

5)

Memory	Data
0100	A
0101	B
0102	C

6) Since r16 is modified to store the result, the question asks to use another register to store it. Use r15 to copy contents of r16 to it, use mov instruction for data transfer.  And use r15 in all the instructions further to add the two numbers.

lds r16, A

lds r17, B

mov r15,r16

add r15,r17

sts C, r15