Need help reading a schematic.

[stj]

Re: Need help reading a schematic.

http://6502.org/

[stj]

Re: Need help reading a schematic.

yes, very easy on 6502, one accumulator, 2 index registers, both 8bit.
only about 50 instructions - half of them you wont use.

just remember that the stack is in low ram - dont write into it!!

[Spork Schivago]

Re: Need help reading a schematic.

first and most crucial thing to writing in assembly or hex is a full and accurate memory-map.
because you arent going to be referencing or linking someone elses library's!

none of that stdin crap etc.

Okay. That makes sense. Learning the instruction set would be the second most crucial thing to writing in assembly?

[stj]

Re: Need help reading a schematic.

first and most crucial thing to writing in assembly or hex is a full and accurate memory-map.
because you arent going to be referencing or linking someone elses library's!

none of that stdin crap etc.

[Spork Schivago]

Re: Need help reading a schematic.

to do the moving dot thing is easy,
set a couple of variables in memory for X & Y
write a character to (videoram+X+(Y x line-length))
start a loop
read the keyboard interface
if it wasnt a cursor key, loop
overwrite the character in (videoram+X+(Y x line-length))
add / subtract from X or Y
write the character in (videoram+X+(Y x line-length))
loop

obviously a delay in the loop or it will be running in mega-turbo speed!

Yes, I understand the pseudo code all right. I can write it in C for the PC just fine. My trouble was with the assembly part of it and the whole CHR-ROM / CHR-RAM stuff. The assembly tutorials I found for the 2A03 weren't very complete. I think maybe they're designed for someone who already knows assembly for the 6502. Mainly, I was following the wiki located here:

http://wiki.nesdev.com/w/index.php/Programming_guide

If you look at the Programming Basics section, you'll notice a lot of To be writtens...

[stj]

Re: Need help reading a schematic.

obviously you would do some boundary checking on X and Y values so you cant go off-screen.

[stj]

Re: Need help reading a schematic.

to do the moving dot thing is easy,
set a couple of variables in memory for X & Y
write a character to (videoram+X+(Y x line-length))
start a loop
read the keyboard interface
if it wasnt a cursor key, loop
overwrite the character in (videoram+X+(Y x line-length))
add / subtract from X or Y
write the character in (videoram+X+(Y x line-length))
loop

obviously a delay in the loop or it will be running in mega-turbo speed!

[Spork Schivago]

Re: Need help reading a schematic.

is that a Rockwell processor?

Technically, I think the CPU the NES uses is a Ricoh 2A03. I believe it's just a modified version of the MOS 6502.

Originally, MOS developed it then Commadore bought it and sourced it to Rockwell and Synertek. After that though, a few other companies got access to it. I don't know who though. Chuck Peddle's team at MOS developed it.

[Spork Schivago]

Re: Need help reading a schematic.

yes, it would.

btw, i can write 6502 assembly.

Yeah, turns out other people have already made some multi-carts for the NES. It looks like it'd be a huge project, software wise at least. I'd need to write the mappers and I don't really want to do that.

On a side note, when you say you can writ 6502 assembly, can you write code that the NES understands or code that an NES emulator understands? The code is a little bit different from the code for a pure 6502 (not Nintendo's modified 6502). I write some code once for an NES emulator. All it did was display a dot on the screen and if you pressed the over button, it'd move over. If you pressed up or down, it'd move up or down. My friend was supposed to work on the graphics but he never did. I struggled a lot with the graphics part of it. I didn't research it much because he was supposed to but the sprite editing program I found was a bit confusing. If you can write code for the NES, what do you use for drawing the sprites?

[stj]

Re: Need help reading a schematic.

originally.

[keeney123]

Re: Need help reading a schematic.

yes, it would.

btw, i can write 6502 assembly.

is that a Rockwell processor?

[stj]

Re: Need help reading a schematic.

yes, it would.

btw, i can write 6502 assembly.

[Spork Schivago]

Re: Need help reading a schematic.

Here's a little info on one of the NES mappers and how it works in regard to banking. Would that make the NES ROMs banking ROMs?

http://wiki.nesdev.com/w/index.php/MMC1#Banks

[Spork Schivago]

Re: Need help reading a schematic.

the way he did it is interesting.
it could theoretically be ported to any 8bit system with games that arent banked.
you would need to re-write the selector-menu for the host system.

i think master system may be a problem, i think the roms are banked - i know nothing about snes - isnt it a 16bit version of a 6502?

I believe the SNES uses a 5A22 CPU based off of the 65c816 core which is an enhanced version of the WDC 65C02 8-bit MPU. The WDC 65C02 8-bit MPU is actually a CMOS enhancement of the 6502 NMOS MPU. So yeah, it is. THe selector-menu might not be that hard. I used to be a system programmer before my brain broke. Anyway, I just need a refresher for C. Learning new languages usually isn't that difficult. The only reason I struggled I think with the NES assembly for the 6502 was because I couldn't find any books on it. The NES used a modified instruction set I believe but it was really hard finding good documentation on how to write an NES game. I found plenty of examples, but I couldn't really find any that actually explained what the code did. Mostly, okay, make sure your code contains this at the beginning: <blah>.

I still don't have a Master System so I'm not too interested in that right now. The NES would be the main one. Maybe you'd like to try and tackle it with me sometime? You work on modifying the hardware, I'd work on writing the code. I'd pay for the supplies if it didn't turn out to be too expensive. Maybe we could sell them and split the profits or something or just release it open hardware for others to use?

One last thing. What do you mean by banked games? Do you mean pages that can be remapped to different internal ROM banks?

[stj]

Re: Need help reading a schematic.

Hey STJ, do you think you could design something like that for the NES and the SNES or no?

the way he did it is interesting.
it could theoretically be ported to any 8bit system with games that arent banked.
you would need to re-write the selector-menu for the host system.

i think master system may be a problem, i think the roms are banked - i know nothing about snes - isnt it a 16bit version of a 6502?

[Spork Schivago]

Re: Need help reading a schematic.

Yes, it is a good way to proto-type a board as it is easy to unscrew the wire wraps to change the circuit connection. Only problem is that it is only good for about 2 years as the connection start to oxidize. With a wire wrap gun many connections can be made quickly. With soldering every time one un-solders and re-solders a joint it weakens that joint. Wire wrapping the wire actually cuts into the post.

Wow, so people still wire wrap? That's cool to know. I got a bunch of bread boards left from when I took Digital Logic back in college. I still use them for projects when I'm trying to learn how to make circuit boards. What's nice about the bread board is I can easily modify a circuit. You know, make changes and then see how the changes affect the circuit. I bet I could do that with wire wraps as well. I was thinking about it last night, and perhaps wire wrapping might make it a little easier for me to follow how the electricity moves through the circuit. I still struggle with that a bit when it comes to parallel circuits.

[keeney123]

Re: Need help reading a schematic.

Are you talking about stuff like this?

https://upload.wikimedia.org/wikiped...ormat_1977.jpg

That's freaking old school! Wow. Do people still do that stuff? I got an old tube amp I'm supposed to fix for my buddy that's wired that way.

Yes, it is a good way to proto-type a board as it is easy to unscrew the wire wraps to change the circuit connection. Only problem is that it is only good for about 2 years as the connection start to oxidize. With a wire wrap gun many connections can be made quickly. With soldering every time one un-solders and re-solders a joint it weakens that joint. Wire wrapping the wire actually cuts into the post.

[Spork Schivago]

Re: Need help reading a schematic.

someone elses.
i do have one in storage,
may have to dig it out because i just found this:
http://spritesmods.com/?art=veccart&page=1

Hey STJ, do you think you could design something like that for the NES and the SNES or no? You seem to be a lot more knowledgeable than I am at this stuff. The original NES is my all time favourite console. The Sega Master System is pretty darn good too though. SNES had nice graphics. I can't play the newer game consoles, they give me seizures for some reason. Even watching for a few minutes, I get really sick. But I can still play the old ones!

Also, with the design that the guy created on the site you linked too...I see he decided to go with assembly for the firmware because he said it gave him finer control of the functions he was executing. I'm fairly good with C. Not so much with assembly but I'm sure it wouldn't take too long to improve my Assembly knowledge. The assembly he's using is for the microcontroller, not the Vectrex, right? I had trouble learning assembly for the 8502 that the NES uses.

[stj]

Re: Need help reading a schematic.

Do you get to keep it or is it someone elses?

someone elses.
i do have one in storage,
may have to dig it out because i just found this:
http://spritesmods.com/?art=veccart&page=1

[Spork Schivago]

Re: Need help reading a schematic.

just put the tv news on for 10min's that will get you angry for a week!
dont overdose!!!

LOL! Yeah, we actually try not to watch the news. It just seems in this country at least, violence sells. We never see anything happy on the news. Always the worst of the worst or mud slinging when election time comes around.