8 bit microprocessor code refresher (assembly programming)

It has been long since I looked at the lowest level programming, probably first since 2000.

Problem / assignment

int i =  14

int j = 28

printf (“%d”, i + j)

result -> 42

4 bit mnemonic table used on 8 bit processor:

0	0	0	0	NOP	No operation
0	0	0	1	LDA	Load data from given memory address into register A
0	0	1	0	ADD	Add register A with given address and store the result in register A
0	0	1	1	SUB	Subtract A with given address and store the result in register A
0	1	0	0	STA	Store register A data into given memory
0	1	0	1	OUT	Copy register A to output (display)
0	1	1	0	JMP	Jump to PC to given address
0	1	1	1	LDI	Load value into the register A
1	0	0	0	JC	Jump is carry is set
1	1	1	1	HLT	Halt the execution

Binary code version:

Address	Instruction (mnemonic)	Data
0	LDA	4	Copy address 4 data into A
1	ADD	5	Add address 5 data with A and store in A
2	OUT		Display the A data [ replacement of ‘printf’ ]
3	HLT		Halt the execution
4	NOP	14	14 value at address 4  [replacement of ‘int i = 14’]
5	NOP	28	28 value at address 5 [replacement of  ‘int j = 28’]

Thanks for Ben Eater  for sharing this video:

https://www.youtube.com/watch?v=9PPrrSyubG0]

Screenshot of same from video.