ZZ80MB, a Z280-based SBC

Description

This my 4th Z280 design. In this design, I want to make Z280 more accessible to general hobbyists so all components are through-hole parts and glue logic are common TTL logic. Another hobbyist-friendly feature is no external EPROM programmer is needed to program the on-board EPROM. ZZ80MB has a "self programming" feature that can serially bootstrap even with a blank EPROM and load the necessary files to program its blank EPROM. Afterward it can boot up normally with the freshly programmed EPROM. The pc board is in the inexpensive 102mm X 102mm form factor. All parts for this board are readily available for about $35.

Files

ZZ80MB_rev2_BOM.pdf

Build of Materials for ZZ80MB, rev 2

Adobe Portable Document Format - 41.66 kB - 10/23/2020 at 12:02

Preview

ZZ80MB_Rev2.zip

Gerber photoplots of ZZ80MB, rev2

x-zip-compressed - 29.00 kB - 10/23/2020 at 12:01

Download

ZZ80MB_r2_scm.pdf

Schematic of ZZ80MB, rev2

Adobe Portable Document Format - 39.08 kB - 10/23/2020 at 12:00

Preview

Project Logs

Collapse

Pictorial Assembly Guide for ZZ80MB
Plasmode • 10/31/2020 at 01:19 • 0 comments

This is a series of photographs showing how to assemble ZZ80MB.
Start off with bare pc board, component side & solder side.
I like to assemble a board with the lowest components first. This way, I can insert the component, flip it over, and use the weight of the board to keep the components flat against the pc board. So first group of components are through-hole 1/8W resistors.
Next is capacitors and a diode.
IC sockets, SIP resistor, and serial port header.
Two RC2014 expansion connectors are next
Last are PLCC socket, reset button, voltage regulator, 10uF tantalum cap, and power plug
CF adapter is quite tall, so it is assembled last. Here is ZZ80MB all assembled and populated.
I will cover programming and testing of ZZ80MB in next blog
Introduction to ZZ80MB
Plasmode • 10/23/2020 at 13:06 • 0 comments
Z280 has two modes of operations. In its native mode, it operates with 16-bit data bus and 24-bit of address. Z280 can also operate in Z80-compatible mode where it has a 8-bit data bus with 24-bit address, but only 64K of memory is accessible at any given time. In ZZ80MB Z280 is operating in Z80-compatible mode.

While Z280 was not a commercial success (too slow, too late), it contains many modern CPU features such as MMU, DMA, cache, and on-chip peripherals. One unusual feature of Z280 is its "serial bootstrap" function where it can be configured to boot without ROM through its serial port. With serial bootstrap, it receives 256 bytes of serial data and save them to memory location 0x0 to 0xFF. When the 256th byte has been received, it starts program execution from location 0x0. ZZ80MB utilizes the serial bootstrap function to load an EPROM programmer that can write the subsequent software into on-board EPROM.

Features of ZZ80MB are:
- Z280 CPU configured to Z80-compatible mode running at 24MHz with bus speed of 12 MHz
- 1/2 megabyte of RAM
- 1/2 megabyte of EPROM
- An internal UART at 115200 baud, odd parity, no handshake
- Two modes of operation:
  - Serial bootstrap mode, loading file from the serial port,
  - EPROM bootstrap mode.
- CP/M 2.2 and CP/M 3 ready
- 44-pin IDE interface for compact flash drive
- Two RC2014 expansion connectors
- Economical 2-layer 102mm X 102mm pc board.

View all 2 project logs

Discussions

Baglio Tabifata wrote 12/10/2020 at 07:41

The rev.2 board presented in this page is out of date and, according to the developer, has an unsolvable hardware bug. Do NOT print it, you can find the rev.3 here: https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:zz80mb:zz80mbr3

Are you sure? yes | no

Todd Decker wrote 11/12/2020 at 17:03

@Plasmode this is an interesting project and may be perfect for my own interests in building a tool chain from the "ground up" the hard way... boot loader, monitor, permeative assembler, editor, compiler, etc. I am thinking about crafting a stand-alone "virtual paper tape reader and punch" that could serial connect to perhaps this and also the 1802-based "membership card". Are you on the RC2014 list? Would you be interested in assistance in this project? And, what are your thoughts on a terminal for your board? Will it have two UARTs, one for the serial port of bootstrapping and another for say the VT-132 VT-100 emulator RC2014 expansion board?

Are you sure? yes | no

Plasmode wrote 11/13/2020 at 00:29

Hi Todd,
I'm Bill Shen on Google Group RC2014-Z80. I'm also active on Google Group retro-comp which is closely related to RC2014, but with more advanced topics. In fact, I have started a discussion topic on ZZ80MB. https://groups.google.com/g/retro-comp/c/5sJDPVfEZgI

Z280 has only one UART although there are RC2014 expansion slots to add more serial ports. While the Z280 serial port is used for serial bootstrap, once the on-board EPROM is programmed and running, the serial port is available as the CP/M terminal, so it can certainly drive VT132.

I have discovered a bug on current version of ZZ80MB, revised pc board is being fabricated at JLCPCB. I should have it back next week. If you are in USA, I can send you a complimentary PC board and a Z280 and hopefully you have parts to fill in the rest.

Are you sure? yes | no

parkview78 wrote 10/29/2020 at 11:02

Back in the early 1990's, I spent many wonderful evenings designing and building a Z280 demo board: http://www.bdug.org.au/project/computing/Z280 I wonder how small it could now be made using SMD components?

Are you sure? yes | no

Plasmode wrote 10/29/2020 at 12:25

Z280 is only available in 68 PLCC, so that limits how small the board can be. I have a relatively small Z280 SBC operating in its native 16-bit mode and with 2 meg of DRAM, CF disk in 75mm X 100mm 2-layer pc board. https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:z280rc

Are you sure? yes | no

parkview78 wrote 10/30/2020 at 00:26

A nice board! Thanks for the link.

Are you sure? yes | no

Plasmode wrote 10/29/2020 at 12:35

BTW, thank you for your Z280 manual. That's the one I used, the 2 missing pages were patched in by the time I've downloaded it.

Are you sure? yes | no

Ivan Stepaniuk wrote 10/29/2020 at 10:10

64K ought to be enough for anyone :P really neat project!

Are you sure? yes | no

ZZ80MB, a Z280-based SBC

Description

Files

ZZ80MB_rev2_BOM.pdf

ZZ80MB_Rev2.zip

ZZ80MB_r2_scm.pdf

Project Logs

Collapse

Pictorial Assembly Guide for ZZ80MB

Introduction to ZZ80MB

Discussions

Similar Projects

Reverse Engineering Soneplex SPX-MPU SBC

Generic 8-bit Processors Prototype (G8PP)

STEbus Z180 board

Varian Vista-based Z80 Microcomputer

ZZ80MB, a Z280-based SBC

Become a Hackaday.io member

Just one more thing

Description

Files

ZZ80MB_rev2_BOM.pdf

ZZ80MB_Rev2.zip

ZZ80MB_r2_scm.pdf

Project Logs Collapse

Pictorial Assembly Guide for ZZ80MB

Introduction to ZZ80MB

Enjoy this project?

Discussions

Become a Hackaday.io Member

Similar Projects

Reverse Engineering Soneplex SPX-MPU SBC

Generic 8-bit Processors Prototype (G8PP)

STEbus Z180 board

Varian Vista-based Z80 Microcomputer

Does this project spark your interest?

Report project as inappropriate

Send message

Remove Member

Project Logs

Collapse