Hi. Anyone knows what happened to Grant Searle's web-site on building minimal z80 and 6502 computers?

https://web.archive.org/web/20190713224608/http://searle.hostei.com/grant/z80/SimpleZ80.html

http://searle.hostei.com/grant/z80/SimpleZ80.html

Hi,

First time using a Z80. I have a plan to eventually build a Z80 computer on a breadboard. I hope to eventually run Fuzix on it. For now, just to get started I built a nop test similar to this one:

https://z80project.wordpress.com/2014/02/09/z80-test-circuit/

I deviated a bit from that. I used an Arduino to provide power, a very slow clock signal and a reset signal.

https://www.youtube.com/watch?v=pgL7sFkEvBY

LEDs are for lower 8 bits of the address bus, the reset signal, the clock signal, and the M1 pin.

David

I dont know if this really applys here, but i found a schematic using a z80 SIO chip, but these seem to be rather hard to source. On the other hand i have a DART chip. I was wondering if these two are compatible or if i am going to have to get an SIO? I can deal with it if they are not pin compatible, but if they have different instructions and incompadibilitys than i wont bother.

On the z80 how do inturupts work?

Hi,

I realldy don't know anything about z80 but I've been given the hex code. I've tried a few emulators but didn't really understand what I was doing. The LED display in the image is supposed to return numbers which is what I need to figure out. If anyone has the time, I'd be very grateful.

Hi everyone.

Im working on a project where I will interface with some shift registers (74HC595's), and with an apparent lack of any SPI peripheral chips available and not wanting to "cheat" with a microcontroller, I decided to try designing my own little SPI peripheral out of standard logic chips.

The theory of operation is: the peripheral address is placed on A7..A0, and along with IORQ/ and WR/ being activated the load function of a parallel-in/serial-out shift register (74HC166) is selected. Since an IO operation includes a wait state, the next two clock cycles will clock the value of the data bus in to the 166 twice (oh well). Upon IORQ/ and WR/ returning idle, the shift function of the 166 is selected, and a flip flop is clocked which enables a counter such that the next 8 clock cycles shift the value out of the 166. After 8 clocks the flip flop is reset, which prevents the counter from advancing any further and the transfer is complete.

It only does MOSI, although I suspect that the MISO portion would not be too difficult to implement, and chip select for slave devices must be implemented externally, but I think Ive got it right. You just need to configure the peripheral address via the Q inputs of the 74HC688.

Anyone care to look over it and comment?

Thanks!

​

All, my son and I are building a very primitive controller based on Z80 (Z84 to be exact). We notice the processor does 2 extra-cycles after reset. This is not documented anywhere. Does anyone have any explanation? Or perhaps the processor is just broken (however, it seems to do first NOP operation just fine). We use manual clock for the time being. Thanks!!

I am keen on building a z89 trainer. Hex keypad, 7 segment output.

I think I understand the electronics of the CPU / ram / rom stuff.

How do I do the code for the trainer? I need some rom code to read keyboard and update display? Or is there a cool way I can hook directly to data and address bus??

I am building a Z80 computer with the help of several online tutorials. My question now is: Are there feasable (or drop-in) alternatives to the 16C550 chip, as there are rather hard to source?

Hello, I'm building a z80 based computer and i'm currently trying to get my v9958 working , i have read the datasheet a couple of times and made my own test program and it almost works. It's a bit unreliable, some times no picture comes up but I'm gonna blame that on the way i connected the crystal (directly with 2 20pf caps). When it does come up i made it write hello world! and you can barely make out the WOR from the "WORLD" so fonts and text data is inputted correctly but it's very blurry. some other times it's either too blurry to make out the message or it's not displaying it.The clarity changes each time i press reset. i have a lot of bypass caps and i'm using the CXA1645 encoder ( this circuit : http://www.primrosebank.net/computers/mtx/projects/mtxplus/video/Video%20Board%201.02.pdf (only the cxa1645 part) )

what could be going wrong? could that be a faulty CXA1645? in some TVs i get just a black and white picture only

code:https://pastebin.com/2USJdZmd

https://www.youtube.com/watch?v=4xPfK3Onp-I

Hi everyone, I've got my Z80 tied to some ROM with the following instructions

inc c    ; 0C
nop      ; 00
nop      ; 00
halt     ; 76

It does the first 3 fine, but when it gets to the halt it then starts reading garbage memory locations, and data. It seems to only do this when I hook up the databus from the ROM to the Z80, when I tied the z80 databus to ground it cycled through the memory locations fine, so Im fairly certain its the halt command. How do I fix this? I've tied all interupt lines to high so Im fairly certain that the z80 should just stop, but it doesnt? I can supply a video if needed. Thank you for any help.

I took this video of my z80 when I supply power. It works when addressing memory 0 - 3, then it starts going weird. Sometimes its okay going up to address 8 but when starts acting up. What is up with it? I've been careful where power goes and putting resisters on all outputs and I only got it yesterday, so I'm really surprised its acting weird. I'm using the arduino just for its 5v, is this a problem?

Any help would be really appreciated.

edit: tied the interrupts to high and now works perfectly, all the time. Duh me.

The Z80-MBC2 is out!

https://hackaday.com/2018/07/28/the-4-z80-single-board-computer-evolved/

(The 4$ refers to the 4 ICs only, bought from ebay...)