Z80SBC64, Hobbyist Friendly Z80 SBC


Z80SBC64 is a hobbyist friendly version of Z80SBCRC. All components are either in through-hole technology or easy-to-solder surface mount components. The board is in the standard RC2014 (100mm x 50mm) form factor.




  • Z80 running at 20MHz
  • ROMless
  • Battery-backed 128K RAM
  • Altera EPM7064S in PLCC44 package
  • 4 banks, each bank is 32KB
  • Simple serial port with serial bootstrap capability
  • Serial port operates at 115200 N81, no handshakes
  • Compact flash interface
  • CP/M 2.2 and CP/M 3
  • 100mm x 50mm pc board
  • RC2014 bus interface


The heart of the SBC is a 5V CPLD, Altera EPM7064S, that implements the serial port receive function, generates baud clock, interfaces to compact flash, and divides memory into 4 banks of 32KB. The design has no ROM. The traditional ROM software are stored in battery-backed RAM. The serial bootstrap function loads the ROM-equivalent software into RAM when the board is powered up the first time; the system boots off the software in RAM for subsequent power cycles or resets. The ROM-equivalent software are protected by switching to banks inaccessible to normal software.

Instead of the EPM7128S, a smaller EPM7064S is used because it is available in PLCC44 package that can be socketed in a 44-pin PLCC through-hole socket. This is the design compromise to enable a hobbyist-friendly board with through-hole components and an easy-to-solder surface mount connector. Because of the limited resources on EPM7064S, the memory supported is 128KB with 4 banks of 32KB. Furthermore, the serial port transmit function is emulate in software (bit banging).

Design information



Gerber photoplots, the boards were manufacturered by Seeed Studio.

Altera EPM7064SLC44 design file. The design are created as schematic in Quartus 8.1. This is a PDF file of the schematic

Bill of Materials


Z80SBCLD is the bootstrap loader. Configure Z80SBC64 to Serial Bootstrap mode and send Z80SBCLD.BIN as binary file to Z80SBC64 immediately after reset. Z80SBC64 will respond with “Z80SBC64 Loader v0.2” sign on message and ready to receive ZMon64 load file.

ZMon64 is the monitor loaded by the bootstrap loader

cpm22all is CP/M2.2 BDOS/CCP/BIOS for Z80SBC64

XMODEM is the file transfer program to bring in all CP/M programs from PC to Z80SBC64. While in monitor, send XMODEM.HEX as Intel Hex file, type 'b2' to boot into CP/M2.2, then type 'save 17 xmodem.com'. XMODEM.COM will be created as the first file on the CP/M disk. To invoke XMODEM to receive files, type 'xmodem filename /r/c/z1' and go to the terminal program to send file via xmodem.

depkg.com is an utility software that unpackages a collection of files into the original individual files.

cpm22dri.pkg is collection of CP/M 2.2 distribution files to be unpackaged with depkg.com

Instruction and Manuals

Getting started guide

ZMon64 manual

Pictorial assembly guide

builderpages/plasmo/z80sbc64.txt · Last modified: 2018/12/19 10:00 by plasmo
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