Modern Computer Architecture and Organization, by Jim Ledin. Published by Packt Publishing.
Write 6502 assembly code to store two 32-bit integers to addresses $00-03 and $04-$07, then add them, storing the results in $08-$0B. Use a looping construct, including a label and a branch instruction, to iterate over the bytes of the two values to be added. Search the Internet for the details of the 6502 decrement and branch instructions and the use of labels in assembly language. Hint: The 6502 zero-page indexed addressing mode works well in this application.
See the 6502 assembly file Ex__6_32_bit_addition.asm for the 32-bit addition code.
Try running this code at https://skilldrick.github.io/easy6502/