Talk:PPU registers

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Revision as of 21:57, 28 February 2010 by Banshaku (Talk | contribs) (Agree with Blargg on this.)

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Naming the registers

Am I the only one being annoyed by those "PPUMASK" "PPUSCROLL" etc... names ? Because Mr Tepples often refers them as it doesn't mean everyone often refers them as it. I like to use plain $2000, $2005, etc... Personally I'd vote for removing references to those names from the Wiki but I don't want to force it if other people disagree. Bregalad 21:29, 24 February 2010 (UTC)

It depends. It's not only Tepples that promoted those names. I'm a firm believer that using symbolic constants makes the code easier to read. As long both are available in the wiki I don't see the issue.

I can give you an example as code. Which one is clearer when you read back the code?


lda #%1010000
sta $2000


In another file (nes.h)

PPU_CTRL_NMI %10000000
PPU_CTRL_SPRITE8x16 %00100000
PPU_CTRL $2000


Somewhere in the code


Once you know the convention, it makes the code easier to read. Of course for the registers only it could be argued for a while since there is not that much on the nes but it's always good to follow good programming practice. In a professional environment, I will always promote the second once since it makes the code clearer.

You don't know how many time I saw code samples for newb with no comments at all and you have to figure out what the hell was done with anonymous labels to make it worst. At the least those constants give some visual feedback on what you're trying to do. It's only a matter of getting used to the naming convention.

In brief, I think it's a good practice to use them but nobody is forcing you do to so. There's just there to try to make a convention and of course not everyone will agree with it (i.e. see how many linux distro..)

Banshaku 01:35, 25 February 2010 (UTC)

Well it's fun because I always do it like your "bad example" exept I write numbers in hex instead of binary, and I never had problems reading it. Symbolic names just makes the thing longer and more confusing. In fact I think it is the exact opposite of what you said - it makes things harder to read in my opinion. Then it depends if you remember best words or numbers - I know I remember numbers better personally.

Like you said, as long as there is both there isn't any problem... but my issue is that I found several pages on the Wiki which ONLY refers the symbolic names which are nothing official anyways. So my proposal would be to not touch this page, but change the others to mirror the numbers (e.g. $2001) instead of symbolic names that makes few sense (PPUMASK really makes no sense to me it sounds like carnival or something).

Again I don't want to force anything but I'd vote for at least replacing all instances which ONLY have the symbolic names to show the true register instead. Bregalad 08:20, 25 February 2010 (UTC)

I was not aware that some page of the wiki only refer to the name. In that case, yes it can be confusing since there is no official standard for naming them. To make both crowd happy, we could always put both at the same time too.

Which pages are like that?

As for using constants For the registers, the benefit is quite negligible since there is not that much but for flags or your own values in your game, it will save you from many headache when you use the same value many time. Of course, if you use long name and you have to remember all of them by heart, everybody will agree with you and say it's quite a pain in the butt (I do agree) but with a good editor, the editor will give you suggestion once you start to type a word. For example, in Visual Studio, Eclipse and many IDE, if I would type PPU, it would give me a suggestion list of all the words that start with PPU. In the case of nes programming this is an issue because there is no such editor that gives that functionality. I wanted to make one for that reason since I cannot remember all my constants, which is normal.

Banshaku 12:05, 25 February 2010 (UTC)

See GBATEK for the kind of style that I was attempting to follow when I instituted the PPU registers' names in the first place. The GBA community never refers to registers by their address. --Tepples 12:55, 25 February 2010 (UTC)

Tepples there is a big difference : The NES adresses are 16-bit and so you only have 4 digits per adress, which makes them much easier to remember. Another big differences is that all those names are made up - they are nothing official and probably aren't "often refereed as" as this page says Ian Bell uses the following definitions in his open source "tank demo" so if anything were to be official it'd look more like this (and again I doubt it's official it's probably made up by Ian Bell himself) :

VCR:		EQU	$2000	; video control reg base address
VSTAT:		EQU	VCR+002	; video general status register
OAM_ADR:		EQU	VCR+003 ; sprite attribute address register
SCROLL:		EQU	VCR+005 ; scroll h/v registers appear here
VRAM_ADR:		EQU	VCR+006	; video address register
VRAM_DAT:		EQU	VCR+007	; video data register


CONTROLLER1:	EQU	$4016		; Joystick and DMA
CONTROLLER2:	EQU	$4017		; Ports

So according to what Banshaku said, I guess I can go ahead and remove places where registers are refereed only by their GBA-style name and replace them with true adreses. If this cause problems someone can still undo the changes. --Bregalad 15:10, 25 February 2010 (UTC)

Game Boy addresses are 16-bit, yet the same fellow behind GBATEK also wrote Pan Docs. --Tepples 16:02, 25 February 2010 (UTC)

We should just be careful thought. It's not because there is no official naming convention coming from Nintendo that we cannot make our own in the first place. If we go that extreme, we could say that we don't agree with Loopy_V/Loopy_T naming convention because that is not official too.

There is nothing wrong to try to make a naming convention that seems simple for new users. The one shown above is not any simpler the the currently proposed one on the wiki. It's all a mater of preference. Don't forget that people have complained many time that the wiki was "not organized" so we shouldn't shoot down people that try new ideas. There is nothing wrong we that. You may have missed that Ddribin did some example in it's own sandbox for some possible formatting and naming convention here. I thought his idea was interesting and it passed under the radar of everyone.

Banshaku 23:46, 25 February 2010 (UTC)

I just noticed this mass-removal of named registers and it's ridiculous. The point of this Wiki is to make thigs clearer. Using numeric addresses everywhere adds needless detail and harms its primary purposes of educating NES programmers.

The point of using an assembler is to work at a higher level than machine code. The assembler allows you to use the names of instructions rather than their op codes. Likewise, it allows one to give addresses names and work with them. Labels in programs are one example, and named constants are another. If one really believed that using hexadecimal values instead of named registers was good, one would have to argue the same for labels and instructions, and thus use only .byte directives in the assembler.

New NES programmers have plenty to remember already. Being able to say PPUSTATUS instead of $2002 lightens their mental load, and reminds them of the register's purpose wherever it's used, without having to look anything up. Even an experienced NES programmer who takes a break will have to re-learn the values to some extent, and make more errors during the process.

All NES programmers make typos when programming. Making a typo on PPUSTATUS will result in an assembler error in almost all cases, rather than a program that misbehaves. Making a typo on $2002 can easily result in a program that assembles fine but fails to work, without any way to easily find the typo.

When a programmer is reading source, addresses like $2002, $2003, $2005 all tend to look somewhat alike, while PPUSTATUS, SPRADDR, and PPUSCROLL are more distinct, and can be set up as keywords for the syntax highlighter.

If one is used to using numeric addresses, he will have to learn the names for them, but this has none of the disadvantages listed above. The names are based on the function, rather than arbitrary numbers. And misremembering a name will be caught almost immediately. I can't help but think that the desire for removal of names is to avoid having to learn them, or make up for deficient tools or something.

Blargg 22:18, 28 February 2010 (UTC)

It's a battle of the B's, and I'm still the odd one out even after buying a copy of Bee-52 :-)

Martin Korth uses purported official names in GBATEK and Pan Docs, but he appears not to use names in Everynes. My early GBA header files used different names from the names in GBATEK. Part of this was to be different on purpose to avoid appearing to support the use of unlawfully acquired trade secrets. What are "official" names other than names in leaked Nintendo manuals? The other part was to take advantage of the various arrays implicit in the GBA register map. In fact, some elements of my naming scheme, particularly with respect to these arrays, eventually made it into devkitPro's libgba header file, which otherwise follows GBATEK. (See for example BGCTRL[].)

So, Bregalad, do you object to the idea of having the community invent a consistent set of names, or do you just object to the specific names I invented? --Tepples 02:44, 1 March 2010 (UTC)

I tend to agree to what Blargg said. Making a typo on a name will make the compiler fail but a typo on an address won't. By using constant you avoid that possible issue.

For beginners, those constants are a must. How many times when we look at the code sample they send that we can be sure that they really meant $200X and it was not a typo? With the constant, it makes it plain obvious and easier to correct them.

I think it will be hard to make everyone happy in that case. For now, we only have one person objecting to this naming convention. I just checked the updated page and since I didn't program the nes for a while it didn't make any more sense to me anymore. When you have to juggle with many platforms during the day, constants and the proper tools the way to go. If I could find an editor that do some intellisense with my own defined constant I would be happy. I need to check if Notepad++ can do it, that would be great.

Banshaku 03:57, 1 March 2010 (UTC)