P90MB, P90CE201 Motherboard


P90MB is a motherboard based on P90CE201 with 3 RC2014-like expansion slots.



  • P90CE201 at 24MHz
  • 512K PROM
  • 512K RAM
  • EPM7032S CPLD
  • Compact flash interface
  • I2C connectors
  • Three RC2014-like expansion slots
  • CP/M68K ready


Design Information

Engineering Change

A engineering change is required for more reliable CF access. The 8 data pins (pins 3, 5, 7, 9, 11, 13, 15, 17) to the CF adapter are removed and replaced with 8 100 ohm resistors. Similarly the IORD pin (pin 25) of the CF adapter is removed and replaced with a 100 ohm resistor. Even with the engineering change, it will not work with all CF disks. The CF disk that seems to work reliably is CISCO 64 Meg CF disk.




P90MB monitor


CP/M68K distribution files, plus gkermit, microEmac, and BASIC compiler. Unzip and use gkermit to upload to P90MB. The console baud rate needs to change to 9600 baud for gkermit to work.

Lee Davison's EhBasic for P90CE201

EPROM programming file with monitor, CP/M, and EhBasic

Conway's Game of Life running on P90MB. This requires a 128×64 OLED display plugged into the I2C connector. The scenerio running is “Gosper Gun”.



P90CE201 Datasheet

Getting Started with P90MB

Works to be done

  • Kermit file transfer is not working in CP/M68K. The most likely reason is because hardware handshake is required and P90CE201 UART has no hardware handshake signals.
    • XMODEM maybe a better replacement for Kermit
    • Kermit works at 9600 baud, so the simplest solution is to add a command to switch baud rate.
  • CP/M68K's DDT is not working.
builderpages/plasmo/p90mb.txt · Last modified: 2020/08/30 08:04 by plasmo
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