8085-emulator

Emulating an 8085 processor in C++

Specifications -

• 64KB of stack memory (1024 * 64 * 8 bits)

Functional Overview -

• Reset operation
• Fetch -> Decode -> Execute cycle implementation
  • Fetches current instruction from Memory[PC] and stores into the IR
  • Decodes fetched instruction via switch-case
  • If decoded instruction is valid, it gets executed

Abbreviations -

• PC - Program Counter
• SP - Stack Pointer
• IR - Instruction Register
• A - Accumulator
• Z - Zero flag
• S - Sign flag

Future Plans -

• Opcode decoder which can read opcodes from a text file and execute them
• Adding on to above point, syntax checker - proper compiler/interpreter perhaps (?)
• Plan: what to do about the clock cycle parameter ? -> removed cycles as a param
• Fix: unable to print memory[Addr] values
• Updated readme will not specify all opcodes (opcode list will be included) but only specify how exactly the opcodes are implemented here (if any changes)
• Implementation scope -
  • Assembly program for 8085 will be loaded into emulator
  • Assembler/Decoder will take care of parsing opcodes and setting program memory according to parameters passed and number of CPU execute calls required based on number of opcodes decoded
  • Hence allowing for the program to be run seamlessly by simply calling the CPU execute function based on number of opcode count
• Decouple CPU functions and Instruction implementations - write functions to call within instructions to use repeated functionality