In this video, I build a new Flash ROM / RAM board and use it to install the RomWBW CP/M distribution on the RC2014:

I’ve already done one video on CP/M on the RC2014, but when I built the Zeta 2 Single Board Computer, I liked Sergey Kiselev’s design so much that I thought I’d try to adapt it over to the RC2014.

Overview of the new design

The new design, based on the Zeta 2 by Serget Kislev, uses a 512 KB Flash ROM and a 512 KB static RAM. There are two register file chips that implement a 7-bit paging register. This allows you to slice up the Z80’s 64 KB address space into four windows, each of which can point to any 16 KB page in ROM or RAM.

There are several advantages to the new design:

The CP/M operating system and BIOS is built into ROM

ROM disk allows over a dozen CP/M applications and tools

RAM disk allows programs to be downloaded, assembled, etc.

No external storage (CompactFlash or Floppy) is needed for a basic CP/M system

Flash ROM can be reprogrammed without needing to be erased

Schematic

Here’s a picture of the schematic

Implementation

Here’s the board I built

Modifying RomWBW

The CP/M distribution that runs on the Zeta 2 is called RomWBW by Wayne Warthen. Since the RC2014 is not exactly a Zeta2, I had to make a few modifications:

Added support for the Z80 SIO/2 chip

Added support for the ICAI chip (for those using the original RC2014 serial board)

Github makes it very easy to fork an existing project and make available your own changes. My fork of RomWBW is located at https://github.com/sbelectronics/RomWBW

Flash ROM / RAM Board Bill of Materials

Name Description Supplier Pc-board osh park U$2 512K Static Ram AS6C4008 digikey 1450-1027-ND U$3 512K Flash ROM 39SF040 digikey SST39SF040-70-4C-PHE-ND IC1, IC2 74HCT670N register file ebay or digikey 296-33164-5-ND IC3 74HCT139N dual 2-4 decoder digikey 296-8390-5-ND IC4 74HCT138N 3-8 decoder digikey 296-1608-5-ND IC5 74HCT74N dual flip-flop digikey 296-1625-5-ND SV1 2×8 male header RN1, RN2 10K x 5 (6-pin) resistor network digikey 4606X-1-103LF-ND

Board Ordering

As usual, the boards are up on osh park: