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That almost works. What you are looking for is the "EQU" assembler directive. From the ASM6 documentation: EQU For literal string replacement, similar to #define in C. one EQU 1 plus EQU + DB one plus one ;DB 1 + 1 So your example above becomes: aY EQU 10 aX EQU 20 .db aY, $80, $00, aX, aY...

Decoding WRAM with the '139 is pretty simple really. Each two-to-four decoder has it's own /E input. So you put PRG /CE and M2 into the first decoder so that output 3 is low when both are high. Then you loop output 3 back into the /E input for the second decoder. Then put A13 and A14 into the last t...

This is pretty cool! You may find this thread of interest for background collisions. I recently struggled with this myself. For your game you won't have gravity, and your velocities may be constant, but the sequence of steps needed for correct background collision and response is there. Also I admir...

OK, so I've got the WRAM straightened out, and I like using the decoders to enable the PRG-ROM, but I've hit a snag. With the '374 there is no Clock Enable input. So how do I make sure it is only clocked on a write to PRG-ROM? I can't figure out how to make this happen without a hex inverter or some...

Wow, thanks for the tear-down

It will take me some time to wrap my head around this

Edit: UQROM is just what I'm calling UxROM with PRG-RAM. Hi all! As I have mentioned before I know just enough about hardware to be dangerous :oops: I am trying to create a UxROM cart that can support battery-backed WRAM and 4MB of PRG-ROM. Realistically I would never have need of such a behemoth ca...

I'm glad to hear your project is progressing Tepples! What are your plans for it? Will you give away the ROM when you are done or are you going to publish it on a cart?

I'm obviously not familiar with how folks release their games. I am trying to get a handle on it

The ATMega128 is a micro-controller, not a programmable ROM chip. Have a look at the 29F010 (ordering page is here ). This is a Flash version of the same chip that supports programming at 5VDC and can withstand 1,000,000 erase / write cycles. There is also the 29F020 (256K version) and the 29F040 (5...

The pinouts of the ROMs Nintendo used are different than what we have available today. See NES ROM Pinouts.txt and NES EPROM Conversions.txt . And why'd you sack an SMB3 cart? Sure there are a lot of them, but come on man! At least sack a crap game like Gauntlet II or Where's Waldo? :D *sigh* I wish...

This is very impressive! I noticed on your blog you mentioned that you have completed the second boss and the first eight levels. Any chance you could post a video showing those off?

I meant an array of structs is slower and more difficult to program for.

I am using a system that meets your requirements. All sprites are rectangular and no pattern reuse is possible. If these limitations are acceptable then you might consider it. I lay out all of the unique frames of animation in CHR-RAM in sequential order. Each object type has an attribute table that...

I have to agree that even 6 scanlines per object sounds very reasonable if you are doing proper physics and collisions for all of them. A lot of games don't even apply the same rules to all objects, since not all of them need such complex handling. Some objects don't move at all, others are always ...

6 scanlines per object. I have 1 player, 4 mobiles and 11 projectiles possible giving me a worst-case of 96 lines. This does not include AI or object to object collision detection or music. I suppose I could lower the projectile count. This more of a Zelda II affair anyhow. That would help with scal...

I've just written my first update and background collision routine for a new project I am working on. I have never done a platformer before. I've gone over the logic several times, but I get the impression that it is sub-optimal. Could you all help me think this through? I can't seem to find any dis...