Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

The place for codemasters or beginners to talk about programming any language for the Spectrum.
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Nomad
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by Nomad » Wed Feb 14, 2018 2:16 am

Hey Keith,

I have a 23" monitor, and the text in the videos is so tiny its unreadable. Is there not some way you can zoom or maximise the window when your showing the code?

Good on you for having a go at the tutorials but unless your watching it on some huge screen / projector I don't see how you can follow along.
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by Nomad » Sun Feb 25, 2018 10:44 am

I am always curious how other people go about development.. can I ask, do you just go straight in and start coding the projects or do you go through an analysis phase/problem definition kinda deal?

Would have thought doing multi platform projects there would have been more need to study the problem first before jumping in.
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by PeterJ » Sun Feb 25, 2018 11:14 am

Many thanks @keith56 for doing this. You have obviously put a lot of time and effort in. It's all very good stuff.

Would it be possible to calm down the text colours on the website? It's all rather bright!

I could not get your Enterprise 128 page to load

http://www.chibiakumas.com/z80/enterprise128.html

There is a type up of a Enterprise 128 Assembly Language book here. If you use Google translate its possible to get the grasp of it:

http://www.ep128.hu/Ep_Konyv/Gepi_kod.htm

Peter
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by PeterJ » Sun Feb 25, 2018 3:54 pm

Just found 'Print Mode' That looks much better!
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by Nomad » Mon Feb 26, 2018 4:02 am

I would use the whole screen to zoom in on the area that you are currently using and not the whole desktop. That way the font is large enough to be seen easily. Unless you got good eyesight its very difficult to see what is going on with a regular screen.

For example, this fella has the open window zoomed.



Length is fine, better to cover something properly than gloss over something important.

I wouldn't worry about focusing on the Amstrad, as long as eventually you are going to cover the memory map, screen layout, and rom calls for msx I think its not an issue. I think that is the interesting point about doing the ports is showing how to find the equivalent rom calls, adjust the memory pokes/peeks for the various platforms. I don't think that has been covered in a youtube tutorial. Sure it all comes down to RTFM in the end but to show the process I figure that will add a lot of value. :lol:

Nice work so far by the way, it must take a lot of time to prepare.

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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by Nomad » Sat Mar 10, 2018 9:29 am

Nice work Keith,

One thing I have noticed that is a 'barrier to entry' with the CPC stuff is none of the books seem to have been scanned (well English language ones anyway). How are you supposed to figure out the system without the books?

I know cpcwiki is there but its not the same as having the primary source material to look at. Were the books really that worthless that nobody thought it was worth preserving them?

The CPC wargaming book looked pretty interesting but so far as I can tell its not been preserved anywhere.
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by AndyC » Sat Mar 10, 2018 9:38 pm

Nice. I think maybe you missed a trick using self modifying code in the example - it might have been slightly more instructive to pre-stage the HL' register with the address of the colour values and then just let the ISR reset it as and when it needed to. That might have shown another one of the benefits of the alternate register set in that kind of scenario, they can persist values for the ISR allowing you not only to avoid having to PUSH/POP the registers used by the main program, but also to avoid having to reload values needed by your interrupt code.
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by AndyC » Sun Mar 11, 2018 12:53 pm

keith56 wrote:
Sun Mar 11, 2018 7:18 am
It's quite curious how the different systems use the shadow registers
in my game, I use DI/EI when I use the shadow registers in a normal loop, but two EXX 'es and DI/EI are pretty much the same speed as a PUSH/POP, so there's rarely any cases it's worthwhile.
it seems interrupt handlers on most do not alter them, but the CPC does, I wonder what the 'best' way to use them overall is?
I think the Amstrad is using them pretty much as Zilog intended, as a sort of precursor to kernel/user mode separation we see on modern CPUs with one set of registers that "belong" to the system and another for user mode. That best explains the rather "all or nothing" swap arrangement, with AF really being singled out as a way of transferring simple values between the two. It's often difficult to make really good use of them under normal cicrumstances (for the reasons you indicate) but often you see more use in cases where a subroutine needs to juggle just ever so slightly more values than normally fit - that does normally preclude from using them in interrupt handlers though (although sometimes using push/pop there instead is preferable if you don't need the full register range).
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by Wall_Axe » Tue May 08, 2018 5:28 pm

that is pretty interesting thanks

so if a digit is zero and we subtract one, the result will be 255
so does daa fix the result to 9 (and activates the carry flag)?


so daa also allows someone to use nibbles?
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Re: Beginner's ASM Tutorial: Multiplatform Z80 ASM development videos... with vampires!

Post by AndyC » Tue May 08, 2018 6:04 pm

If A was 0, and you subtract 1 (so it's now 255), DAA would reset it to 99 (with Carry).
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