Tiny Z80 - Business Card sized Z80 SBC

[Sergey Kiselev]

This is my attempt of designing a compact, mostly SMD-based Z80 SBC. The board size is 50 mm x 89 mm, similar to a standard US business card size.

It is based on Z80 EIPC (Z84C1516FSG), which contains CPU, SIO, PIO, and CTC.

The computer also includes 512 KB battery-backed SRAM and 512 KB Flash ROM, using 4 x 16 KiB mapper (same as in Zeta SBC V2 / Easy Z80 / RC2014  512k ROM 512k RAM Module). The memory mapper and other glue logic implemented using Altera MAX7000AE CPLD. This is a 5V tolerant, 3.3V CPLD, so the board contains an LDO to provide 3.3V to the CPLD. Alternatively 5V MAX7000S CPLD can be used instead.

For convenience, I've integrated FTDI FT231XS USB to Serial converter on the board. It is connected to the first SIO channel.

The board runs RomWBW, using Easy Z80 configuration with small modifications (SIO and CTC addresses). I'll create a board specific configuration in the near future.

Here is the GitHub repo for the project: https://github.com/skiselev/tiny_z80

[Bill Shen]

Nice to see a design based on Z84C1516.  I think the choice of going all SMD is good one given Z84C1516 is a SMT device.  Compatible with ROMWBW is a nice touch, something I have not implemented in my Z84C1516 implementation.  I found out that while Z84C1516 is rated at 16MHz, it can easily run twice the clock cycle if the memory devices are fast enough.
  Bill

[Rob Gray]

That's a real nice-looking board with everything you need to get started.

[Steve Cousins]

That's a great design. Very nice. You've even included LEDs for serial activity and labels for all the components.

Steve

[Alan Cox]

Nifty and as I already have EasyZ80 emulation bits and Z84C15 bits I've pushed an initial set of support to the rc2014 emulator. I'll test it and stuff when I get more time. As the CF adapter clashes I've moved that in emulation to 0x90 for now, but it also emulates an SD card on the PIO anyway.

Alan

[Denis Hennessy]

Really nice looking design. Did you mean to upload the CPLD files to GitHub?  I don't see them.

Denis

[Sergey Kiselev]

Hi Denis,

I just uploaded CPLD files to the GitHub

Sergey

[Karl Albert Brokstad]

I want to learn surface soldering, and this project is tempting.

Very nice design.

Karl

[Sergey Kiselev]

Karl,

While it is not trivial, this project can be a good one to practice SMD soldering skills.
There are a few videos on YouTube showing how it is done. Generally you'll want a magnifying glass and a good lamp (or a combination of both). Also get some desoldering braid/wick to clean up any excess of solder

-Sergey

[Mark T]

I found a piston type solder sucker works better than desolder braid, just need to be careful not to let the tip of the sucker actually touch the parts, two or three mm gap seems to be ok. Any fine shorts can usually be cleared by applying liquid flux and then reflow the solder with a fine soldering tip.

Mark

[Bill Shen]

Karl,
Don't want to upstage Sergey's excellent TinyZ80, but if you want to practice SMT soldering, you should try the CPLDTIL, https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:cpldtil
This is because it is somewhat "fault tolerant": if CPLD or some LED are not properly soldered, some of the lights may not lit, but the board will likely functional at some level.
  Bill

[Sergey Kiselev]

Actually, that works really well. RC2014 CF card does not care about A7 (don't ask me why), so it works happily with either 0x10 or 0x90.

[Earth Person]

Hello  Sergey,

Holy cow.  What comes out of your noggin amazes me.  Just got done with the Xi8088 and Micro8088. I had to jump on this.  I was thinking of diving into a YAZ180, but I’ll move to this first. Just after I ordered at Oshpark, they offered me swift service for free. I only need to do inventory and see what I’m missing. This will be one great addition.

Sincerely,

William Harrington