For example: there are many parts that output data to the internal data bus. Unfortunately spreading the design has also a disadvantage: I need more parts. Using a backplane has its advantages: future expansions can be realized by just sticking them to the backplane. To connect these cards with each other I will use the DIN64-AB connector and an according backplane. Not being able to make my own PCB's, I spread the blocks as good as possible equally over (now) nine Euro cards (10 * 16 cm). There isn't a real schematic of the interior of the 6502 available (AFAIK), so I had to make my own based on 1) the "internal architecture of the 6502" published in many datasheetsĪnd 2) on how the 6502 behaves when executing commands.įirst I divided the 6502 into functional blocks: In these cases it is the 7406 (no other type exists AFAIK) and the 74ALS573. In such a case I mean another available type. There are exceptions, the 74LS06 and 74LS573 don't exist. So if I mention the 08 or 393, I mean the 74LS08 and the 74LS393. Using TTL ICs this means I will mainly use the 74LS series. Yes, my design can be simplified indeed, but at a cost. On the end of this page I will show you a simpler design. But then I was able to lay my hands on some FlashRAMs and decided to support the 6510 as well. Initially the idea was to support the 6502 only. And my goal is to create one that can replace, for example, the 6502 of a VIC-20 or a CBM 8032. But then I found out that this M02 wasn't able to replace a real 6502. I first was a bit disappointed because I thought that someone else already had built the 6502. Here you also will find the M02, a 6502 clone. Very interesting indeed! It will show you, for example, some processors using relays as logic gates. Some time ago I ran into this site: a ring of self built processors. It wasn't until Intel started the production of the 4004 in 1971 that the one-IC processor was a fact.
![sweet 32 6502 emulator sweet 32 6502 emulator](http://3.bp.blogspot.com/-MZh2BDZBcZw/Tvl6ncv5lCI/AAAAAAAAAE0/ASv7X0fFzZ4/s1600/6502EmulatorDiagram.png)
But in the old days the processor was just 'another' part of the computer and was built from parts available at that time: relays, tubes, transistors and ICs. I met some guys who considered this a bit weird: building a processor only using TTL ICs. It turned out I had to use some other building blocks as well: (E)EPROMs/FlashRAMs. But I found out that that was impossible seen from a practical view of point (the explanation will follow later). Someone had to do that to figure it out the first time.The idea of this project was to build the well known 6502 processor using only normal available TTL ICs.
SWEET 32 6502 EMULATOR CODE
It might be fun and educational to try to figure that out by yourself by watching the code execute. From that you could deduce that ROM addresses would start at $8000. For instance A15 (the highest address) might go only to the ROM. Get the game's schematic and trace the signals from the CPU's address pins. It would also be easy to figure out where the game thinks the video memory lives (We'll spend some time going through that). It would be fairly easy to figure out, for instance, where the game's code thinks RAM should be. Watch the code run in your emulator and figure out what it is doing. If you weren't able to have that information, you could figure it out in a couple of ways: Space Invaders has plenty of hardware information available on the internet. (Or just read the data book, or Wikipedia, or google, or.) The 8080 spec shows that there are 16 address pins on it, so it uses a 16-bit address. If you want to know how much address space a processor has, you could figure it out by looking at its specs. There is some other good info there too, but I don't think we're ready for it quite yet. Video hardware is very simple: 7168 bytes 1bpp bitmap (32 bytes per scanline). Plastic transparent overlay and a background picture.
![sweet 32 6502 emulator sweet 32 6502 emulator](https://cdn.evilmadscientist.com/sites/6502/images/A1_3.jpg)
Interrupts: $cf (RST 8) at the start of vblank, $d7 (RST $10) at the end of vblank. Space Invaders, (C) Taito 1978, Midway 1979ĬPU: Intel 8080 2MHz (CPU similar to the (newer) Zilog Z80) Googling led me here led me to an informative write up that told me how put those files into memory: The invaders.zip ROM file that is around the net has 4 files in it, invaders.e. The author of one of the pages volunteers that the video buffer starts in the RAM at $2400, and also tells us how the 8080's I/O ports are used to talk to the controls and the sound hardware. Combining information from here and here, I learn that the game's ROM is located at address 0, and the game has 8K of RAM starting at address $2000. We are going to use some research to find the game's memory map. The 8080 has 16 address pins, so its addresses will be 0-$FFFF.
SWEET 32 6502 EMULATOR 32 BIT
For old processors, this is either 16, 24, or 32 bit address. All the CPUs have the ability to talk to a certain number of addresses. There is one more detail to cover before we begin to write the CPU emulator. Emulator 101 8080 reference 6502 reference Memory Maps