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Yes, sorry the VCC is on the other side of the resistor and when the base of the transistor is low it pulls dtack low. (I tried to ascii art draw it below) VCC (5V) | (RPin 1) [Pull-Up Resistor] (10kΩ) | +--------- DTACK# (to CPU) | (RPin 2) [Collector] (T Left, 2N2222) | CE# Signal --> [Base Resistor] (10kΩ) --> Base -- [NPN Transistor] (T Middle, 2N2222) | [Emitter] (T Right, 2N2222) | GND

@ This makes sense! Thank you for the explanation! 👍👏👏👏

Yes, I have been looking at that. Certainly not having an error handler for BERR is a problem. One of the hardware issues I've seen is DTACK, but I think I've fixed that part. I'd be interested in your longer comment! I think you can email me?? There should be a link on my youtube profile somewhere. :)

@@Rick62820 I just send you an email. The big issue is lack of a reset PC vector.

I have some plastic phone repair tools I 3d printed. That is a good shout. Thanks.

@Rick62820 You revived my memories. Once I constructed part of pipeline inspection device based on Amiga 600. I replaced kickstart completely with my software. At first I traveled by tram to friendly company who has eraser (sheet metal box with UV lamp) and programmer few times a day...later I almost started living there debugging software and hardware (some information in books were incorrect or outdated in A600 and 68020 case).

Well I wanted to make sure that the stack pointer address was well within the memory range so that I was sure that I wasn't going past the memory range. However you are correct that I am using 32 bit addressing and I need to fix that. Subsequently I found that I have a floating pin and a bus error but I fixed those and I'm still having problems so I'll look at the code and make sure to changed everything to 24-bit addresses and hopefully that will solve my issues.

I expected that an out of range address like $50000000 would cause an bus error. But i tried it just on my home brew computer and it did not. And indeed, an uneven stackpointer will cause an address error. The first line after _start you're move a long but define a immediate value that is a word. How does the assembler interpretate that? Regarding to that odd reset behavior. I did not see a link to a schematic in the description, but the reset and hold line must be simultaneous activated for a reset.

@@meettechniek Out of range addresses aren't checked by the processor, the upper address byte is simply ignored (some old code used this byte for other purpose like tag bits), the processor just checks word and longword accesses for odd address and raises an address error in this case. OTOH, bus errors are signalled by *external* hardware to indicate an invalid address.

The bus error was the floating pin. I have fixed that issue. I am keen to get home and try the change to the memory mapping. I also think I need to change my MMIO mapping because I don't have the full 4megs as it is configured now. These comments and discussion has been super helpful for me!

Yes the bus error was a floating pin, after I fixed that the problem went away. I need some change of address mapping for the MMIO.

Well... Yes and no. By default, MOVE does not alter the flags in the condition code register. It simply transfers the data. However, the MOVE instruction can explicitly alter the flags in the CCR or the status register (SR) if it's used to load a value into the CCR or SR. For standard data transfers (e.g., between registers or memory), MOVE does not change the flags. When MOVE is used to manipulate the CCR or SR directly, it will affect the flags as determined by the operation. So, yes and no. 😂

@Rick62820 I thought about indirect change just like ALU was used to transfer but i probably mixed something in decades old memeories 😉 But if i checked documentation When the MOVE source, destination format is used, the Negative and Zero flags are set as per the data moved, the Overflow and Carry flags are reset to zero and the Extend flag is unaffected. When the MOVE source, CCR / SR formats are used, the flags are set directly from the data. When the MOVE is done with the USP as an operand, no flags are affected."

Some of the pins will require pull up resistors. But I didn't mark them in the pinout. I definitely need them for the reset chip and the watchdog. I didn't know much about these BDM debuggers, so I've had a quick look around, and the only one I could find was ridiculously expensive. So I will not be using that, so it's largely irrelevant whether I use pull-up or pull-down resistors, since I simply cannot afford to purchase one of those debuggers! So I'll have to do it, any debugging the hard way.

Huh?

Never heard of it before. Can you please tell me more? I looked it up and I don't see how that is going to help me to find the MMIO addresses for the gpio pins? Can you explain?

The problem is that it with assembly language it depends on the CPU which you are writing code for. Intel CPU instruction set is different from ARM, which is different from RISC-V, etc. But I can give you some books to check out, for various CPUs and architectures. A cheap Raspberry PI with an ARM CPU would be great for a starter. For the X86 CPU: www.amazon.com/Waite-Groups-Microsoft-Macro-Assembler/dp/0672301555 artofasm.randallhyde.com/ archive.org/details/newpeternortonpr00nort/page/n9/mode/2up (OLD BOOK FOR DOS) For RISC-V CPU's: www.robertwinkler.com/projects/riscv_book/riscv_book.pdf riscv-programming.org/book.html For ARM CPU's www.rigwit.co.uk/ARMBook/ARMBook.pdf 6502 CPU: skilldrick.github.io/easy6502/

@@Rick62820 Thank you so much!

Certainly! Here are some books that can help you learn to make games using C and assembly language: ### Books for Game Development in C: 1. **"Programming Principles in C" by John White** - Provides a solid foundation in C programming, which is essential for game development. 2. **"Game Programming in C++: Creating 3D Games" by Sanjay Madhav** - Although it's focused on C++, it covers many concepts applicable to C as well, including game design and architecture. 3. **"Tricks of the Windows Game Programming Gurus" by Andre LaMothe** - Focuses on Windows game development and includes extensive coverage of C programming techniques. ### Books for Game Development in Assembly Language: 1. **"Assembly Language for x86 Processors" by Kip R. Irvine** - A comprehensive guide to x86 assembly language programming, useful for understanding low-level game development. 2. **"Programming from the Ground Up" by Jonathan Bartlett** - Teaches assembly language programming from scratch with practical examples, including game-related projects. 3. **"Write Great Code, Volume 2: Thinking Low-Level, Writing High-Level" by Randall Hyde** - Provides insights into low-level programming, with a focus on optimising C and assembly code for performance. ### Combined Resources: 1. **"Programming 8-bit PIC Microcontrollers in C with Interactive Hardware Simulation" by Martin P. Bates** - Although focused on microcontrollers, this book includes C and assembly programming, which can be useful for game development on embedded systems. 2. **"Game Engine Architecture" by Jason Gregory** - Offers a detailed look at game engine design and development, covering both high-level C programming and low-level assembly optimisations. These books should give you a good mix of theoretical knowledge and practical skills for developing games in C and assembly language.

Good thing is 6502 is so primitive (compared even to 8080) there is hardly anything to learn 😁 Messing with Z80 assembly in my childhood I was amazed just now how primitive 6502 is in comparison. I can't belueve such an underwhelming CPU with just 4 registers (with only 1 of them being able to hold 16 bit value - the Program Counter) and stack of 256 bytes powered some iconical machines like Atari 800 and Commodore 64. Back in the day I thought 6502 was a superbeast 😂

@@b213videoz it is amazing what was capable on such limited hardware. That's why I would recommend it as a starting point. You can potentially build a mental model to hold all of its state in your head. Obviously, you aren't going to be doing any real heavy lifting especially as a beginner. Once you understand what mem-mapped IO is, and get a feel for how simple operations running one after another extremely fast lead to a usable program, something gets unlocked in your brain. I've been wanting to build a Z80 computer, then read recently that they're discontinuing it... I'm sure that there are/will be some more modern replacements or replicas, but still.

@@adammontgomery7980 Oh please, there are enough of Z80 chips in the world for you to build your computer 😊 You can opt for EZ80 😉 Look, I hear you but I'm dissapointed that on 6502 I just can't easily move a block of memory larger than 256 bytes with one/very few instructions like I would on Z80 or 8086. Stack size of < 256 bytes is just pathetic. But once I was past non-sensical syntax of 6502 (which really reminds me of AT&T x86 syntax) I was able to start hacking Atari 800 games within a week. For Ultima II I even managed to implement joystick support - which was absent (keyboard only).

x86 in all its "ugliness" was the first to ptovide division and multiplication instructions 🤪 I actually like original 8086/8088 assembler. 6502 is such a pathetic thing in comparison. TRUE, 6502 is fairly easy to pick up but writing a non-trivial code for it is a mess. The 6loody thing even isn't capable to copy more than 256 bytes without some crazy code. It's UGLY! Even 8080 is far better than that.

@@b213videoz I'll take Sparc RISC any day :)

Glad you like them. I was planning to do some more but I have had to rebuild my PC and it is taking a while. Hopefully more to come soon.

It doesn't break the phrase up or do reverse pronunciation like Pimsluer. You'd need a human for those sorts of things. It doesn't parse the files, it just takes the collection of files and applies the Pimsluer algorithm to them for space repetition.

I ran the gradint python script by itself. The other script was just to get the audio files.

@@Rick62820 thanks for the response. I think parsing on syllables and/or word boundaries is very doable, but it’ll obviously require a library / pretrained neural network to avoid reinventing the wheel. Now I have a side project in mind, haha

Interesting! If do it I am sure the gradint author would be interested. I certainly would be.

@@Rick62820 well, text tokenizers have existed since a long time ago. Surely with the recent breakthroughs in speech recognition, there should now be speech tokenizers too. Worst case scenario, one would need to train a neural network on one’s language of choice. And if it very occasionally breaks up words incorrectly, it probably isn’t such a big deal after all. And then you can make it accept actual dialogs / audio files created for learners of that language from some traditional courses, break them up into phrases and phrases into segments (words and syllables) and then leverage spaced repetition. Effectively, you would be able to generate an audio course identical to Pimsleur from a bunch of dialogs / recordings

You should try, it isn't as bad as it seems.

Sure. docs.google.com/spreadsheets/d/1-U_KoR50Np_-NEiTvvjjIZ_qJhghyS_Lq9AsIs0wujk/edit?usp=sharing

Appreciate it!

No worries! You might want to look into a program called Lute which does a similar thing but has a pre built Docker image.

To be honest I think there is an expectation that if you know one assembly language you can switch easily but in fact they are completely different languages similar to how Java is visually similar to C. You actually have to teach yourself a new language for every processor.

It depends on what CPU you want to write code for. Unlike high level language like C or Rust the language is different for each CPU because they have different registers and instructions.

Thanks for the answer

If you tell me the CPU you are using I could probably recommend something.

@@Rick62820 I am a student right now. I am too interested in both hardware and software. I want to start learning about this. I am searching (RUclips and browsers,..) about this but I can't find how should I start it. Please guide me

I am using "Intel(R) Core(TM) i3-12100"

In this series I am going to be using a virtual machine since it is more accessible to people rather than one specific board.

Not this series, but that is a good idea and I can do that later.

@@Rick62820 the simply biggest issue with RISCV from an Assembler perspective is the lack of good tutorials for using UART, even a simple SSD1306, Interrupts, WS2812 all of the things a MCU would do in ARM so it makes it difficult to consider.

I will try to do something along those lines. At the moment I am awaiting a serial link cable from china so when I get that I can start doing those types of videos.

Awesome thank you!

That is very odd. It is possible Netflix has changed something, or perhaps Firefox changed. I will need to look into it.

@@Rick62820 Thanks. I downloaded subtitles from "American Conspiracy: The Octopus Murders", Episode 4. What I got was only lines spoken by some characters off screen (on the phone), and some by the narrator. I thought there might be a complementary file with the rest but my search turned up nothing else. Thanks!

No I don't. The thing is that I did this series whilst teaching myself Risc assembly and I did already know some assembly. But I did give links to some free books which you can use to read up on assembly language for RISC. This one is really good: www.robertwinkler.com/projects/riscv_book/riscv_book.pdf

great thanks.

I found a tutorial online for GCC/as assembler online (but it wasn't great) but gave me enough knowledge to get started. There are better tutorials nowadays. One trick I use, and I mentioned it in one of my Risc-v assembly videos is to use the -S switch on the GCC compiler and it will output assembly. So I would write a simple Hello World program in C the compile it with the -S flag and the study the resulting assembly code. It does optimization but it is enough to give you a leg up. In addition the ARM website has a super set of documentation with all the assembly language instructions. Then finally I got help from the kind folks on stack exchange.

@@Rick62820 Thanks a bunch. I'll look around what I can find.

@@callisoncaffrey I dug through some of the links I had and posted them below. ARM offers a free online course called "Getting Started with Arm Assembly Language" that is a great place to start: developer.arm.com/documentation/107829/latest/Assembly-language-basics FreeCodeCamp has a tutorial which covers the basics of assembly language programming, the ARM architecture, and how to write simple ARM assembly programs: www.freecodecamp.org/news/learn-assembly-language-programming-with-arm/ The University of Cambridge has a free online course on ARM assembly language programming. The course is taught by Professor Simon Moore, and it covers the basics of assembly language programming, the ARM architecture, and how to write simple ARM assembly programs: m.ruclips.net/video/gfmRrPjnEw4/видео.html Ghidra: Ghidra is a free and open-source software reverse engineering tool that can be used to disassemble ARM assembly language code. This can be a helpful way to learn how ARM assembly language programs work. I hope this helps!

@@Rick62820 No Ghidra for OpenBSD. Though I think I have enough content with the links you gave me. Thanks again.

Mhm i have zero knowledge about ARM CPU. I use a DosBox emulator app on my android tablet. In DosBox we can control a lot of hardware components with x86 assembly 80386/80387 for 32 bit CPU/FPU complex instruction set. Intel developer manuals and documentation from AMD are online. Table with interrupt numbers online (for many bios and DOS function) based on Ralph Browns Interrupt List html version.