For I/O requests, the Z80 actually does put a complete 16-bit value onto the address bus. For simple I/O instructions like in A, (n) and out (n), A the CPU puts the contents of the A register onto the high 8 bits of the address bus and the immediate value n onto the low 8-bits of the address bus. The instructions out (C), A and in A, (C) put the entire contents of the BC register onto the address bus. So, while this is undocumented, the Z80 actually did have a 16-bit I/O address space.
I'm really, really loving your videos. I ended up with a tube of z80s a few months ago and have been dying to do something with them. Thanks for making this so clear and easy to follow along. Looking forward to more.
@@Pony80 always! It can be hard making videos without that positive reinforcement to keep it up. Is the plan to build the whole system on a breadboard before moving it to PCBs? (I mean obviously you have, but in terms of the discussion of the operation.) Also I was wondering why you went with the 14 rather than the 4, I assume the scmitt trigger was to help clean up the clock signal a bit?
In my first build, I converted breadboards to PCB to keep the wires under control. Replicating the 16-bit address bus and the 8-bit data bus to each breadboard was becoming unmanageable. I will probably do the same here, create the backplane, and each card as it is proved out on the breadboard. Also, to be honest, I used a 14 because I had it on the bench. I just did some comparisons with the 04 and the 14 and it didn't make too much different on the clock signal. Good catch tho... Keep me honest!
@@Pony80 If I'm honest I'm fairly new and wanted to make sure I hadn't missed something obvious! I'm currently making the Ben Eater cpu and yeah, unmanageable is one word for it!
I'll very much enjoy seeing where you go with this! I have a few Z80's I tinker with, working on a similar project myself in my spare time. Eventually I'll recreate the 80's computer I never had, probably Spectrum compatible. At the moment I'm using a PIC microcontroller to 'emulate' the bus, for clock, memory and serial IO. I'm planning to expand with physical ROM & RAM, eventually a graphics output. Trying to figure out which components to use nowadays, and how complex I want to make it. I still need to fully understand how bank switching works, it seems the sensible way to go today. John's Basement channel has some great videos and Grant Searle's original Z80 homebrew computer webpage, both an excellent source of info. Good luck! May the magic pixie smoke stay contained!
Thanks!! I plan on implementing bank switching for the memory. I didn’t have it on the first one I made. EEPROM chips are harder to come by these days. I have a bunch on order that are due in August of 23!
I am planning to make a simple 8bit game console (just learning stage) your videos make me easy to understand, so please upload more microprocessor videos :)
Wasn't the 'down to zero Hertz' referring to the original Z80, not any modern model ? I was always led to believe that the 'fully static' was emergent, and not a design requirement. I seem to remember that you can stop the clock, but only in the high state, something to do with internal bus drivers being partially asynchronous. Someone else on YT tried it but stopping the clock caused addresses to jump.
Watching your video, I don't see any markings of any kind on the z80 chip itself. I know that the pin designations on the block diagram of the chip are not where they are on the actual chip. So, with that in mind, how does one know which pins are which on the chip itself ?
On the left hand side of the chip in the video, you can see a semicircular cutout. That indicates pin 1 is on the bottom left. Then it goes in order from 1-20, left to right, on the bottom, and then 21-40, right to left on the top side.
Thank you for the project! I am interested in building it to serve to its original purpose: embedded systems and robotic applications! I wonder which pins work as gpios and how call that "port" in the assembly code. A capture and compare mode is available with for ultrasonic sensors and PWM generation?
I talked a bit about utilizing ports in the memory module video, because we use a port to turn the ROM off and on. I will also be talking about it a lot more in the upcoming LCD video. That should be out this weekend.
"which pins work as gpios" A Z80 microprocessor doesn't have any GPIOs or peripherals (capture & compare or PWM). You'll find those in a microcontroller, with flash and RAM.
couldnt figure out why my computer didnt work, finally realised that just because my clock signal was blinking it dosent mean that the chip was getting a zero when the light went off so i tied it trough a resistor and now ram rom and cpu works just fine.
65536 IO, there are some 16 bit IO instructions. HD64180 10MHz Z8S180 33MHz the above have very nicel inbuilt DMA MMU CNC serial. Z86 series can do Harvard or von Neuman if desired.
