superzazu / 8080

A complete emulation of the Intel 8080 processor written in C99.

Emulation

• 💾 Intel 8080 CPU
• 💾 Z80 CPU
• 💾 MOS Technology 65(c)02 CPU
• 🕹️ Space Invaders
• 🕹️ Pac Man
• 🕹️ chip-8
• 🧠 brainfuck

C libraries

• 📺 SDL_DBGP: a C99 library to display ASCII text in SDL2 programs (in a VGA-like text mode)
• 🖼️ SDL_QOI: QOI image decoding and encoding for SDL2 in C99
• 🔊 SDL_nmix: a lightweight stereo audio mixer for the SDL2

8080's Issues

Incorrect cycles?

Most likely just a typo. In the cycle table, the cycles for XCHG is listed as 5, when it should be 4.

Or, the cycles for "CALL adr" should be 17, while the table only adds 11.

Consider changing the CP/M printing subroutines

Another thing from Discord.

Currently you use ports to print stuff in the CP/M subroutines.

You could change this to something else for readability's sake. At the very least I think it'd make sense to change the subroutine using IN to use OUT, which makes more sense. (Especially since the input you get in that port is hardcoded to 0xFF now, for some reason.)

Add proper disassembly

We talked about this on Discord, but just plonking it here for posterity.

It'd be nice if the disassembly in the debug output was an actual disassembly, ie. that it produced working assembly code. Right now you only print placeholder characters for immediate values, for example.

Apparent bug with the ANI instruction?

According to the manual, the ANI instruction clears the carry flag and the half flag (auxiliary flag). This isn't done in i8080.c (case 0xE6). I suggest adding c->hf = 0 at case 0xE6 to reflect this. It still passes all the test with this added, but it was just a discrepancy between my emulator and yours.

Simplified "self-referencing" for functions in a structure

I really appreciate your work. I am using it to build an 8085 emulator of my CP/M project.
Two minor issue you may want to look at:

1. A simplified way of using "self-referencing" functions in a structure. Have a look at my version of your header file.
   i8085_h.txt

2. Pretty minor but the 8080 interrupt can handle one, two and three byte opcodes. Your code only allows a single byte opcode.