Note: The Banked Memory Expansion Card is supplied in Kitset form only (assembly required). The base price is for the double-sided silkscreened Banked Memory Expansion Card PCB ONLY. The Optional Packs provide all of the components for a complete Kitset. See BOM below (and photo).

What is Minimalist Europe Card Bus

Europe Card Bus (ECB) is a Retro CPU Bus standard from the late 1970’s / early 1980’s.

The “Minimalist Europe Card Bus” (as I’ve called it), is a Retro 8-bit CPU Bus and PCB design standard that I decided to define & document. The purpose of which is to provide a modular platform for me to re-experience the fun of experimenting with the different 8-bit CPU’s, and the various Video and Peripheral devices, that I grew up with in the late 1970’s and early 1980’s.

My goal is that of a robust and modular Design Platform which allows me to create interchangeable PCB cards, based on time proven reliable bus connectors and modern low-cost prototype PCB manufacturing.

i.e. A robust, flexible, and low cost way for me to re-create some of the early microprocessor circuits, that I’d originally built using Wire-Wrap methods, back in the day.

As evident from the name, the Bus itself is based on a Minimalist implementation of the original Europe Card Bus (ECB) standard.

Standardised Mechanical Specification for a Minimalist ECB “MECB” Board

MECB Standardised Board Design Parameters:

• Satisfy the 100mm square maximum board size, for low-cost prototype PCB manufacturing.
• Utilise the lower cost 64-pin (Row A&C) DIN 41612 type C connectors, for cost saving.
• Ensure the DIN 41612 connector(s) can be easily centred across the board width, grid aligned.
• Provide two standardised corner holes, on the edge opposing the right-angle DIN connector, to allow for attachment of card handles (to ease board insertion & extraction), or for board mounting – refer next point.
• Provide an additional two standardised corner mounting holes on the edge with the right-angle DIN connector, to provide a full set of four corner holes (to allow for stand-alone board mounting).
• Standardise PCB corner rounding, for sharp corner removal consistency across all boards & visual tidiness.

MECB Standardised Board Design Notes:

• PCB layout is designed utilising 0.127mm (5.0 mils) grid setting.
• Board size is 99.822mm, which represents the greatest even multiple of 0.127mm (i.e. multiple of 0.254mm – 10.0 mils), that will fit within the desired maximum 100mm board dimension.
• Standard M3 sized mounting holes were chosen. An additional two mid-edge located mounting holes are specified for Backplane boards only (to provide additional mechanical support).
• For reference, DIN 41612 connectors can utilise standard M2.5 mounting bolts (8mm length for the straight connectors, 10mm length for right angle connectors).
• Implemented as KiCAD Templates, to assist enthusiasts by simplifying the creation of each new MECB board design.

Please refer to the attached photo outlining all dimensions for the MECB Standardised Board Mechanical Specifications.

MECB Banked Memory Expansion Card

Why?

I wanted a flexible way to add a Banked (or Paged) Memory Expansion solution, for use with any of the MECB 8-bit CPU Cards.

This would allow exploring larger memory applications, than is possible with the 64K addressing limit of the original 8-bit CPUs.

This might include exploring one of the established 8-bit Operating Systems that is available for the various retro 8-bit CPUs.

Or, it could be simply for implementing your own larger memory model based application.

I had originally been thinking of just a Z80 based paged memory Card, but on reflection, I realised that this wasn’t staying true to my original intent for MECB.

As a reminder, the intent of MECB is, first and foremost, to be a platform for experimenting with the different original 8-bit devices.

It is also intended, to be a platform where you can mix-and-match different CPU Cards with different Peripheral Cards (using it’s bus backplane), to build whatever system you might like to put together.

So, in summary, you can use this Banked Memory Expansion Card with any of the MECB 8-bit CPU Cards, to expand the possible applications of your 8-bit CPU Card with up to 3.5MB of RAM availability.

What You Get

To satisfy different people's needs, I've split the Banked Memory Expansion Card Kitset into Optional add-on Packs.

Firstly, note that the base price is for the double-sided silkscreened Banked Memory Expansion Card PCB Only.

Then, you can add the Optional Packs that might be helpful to you. Adding All the Optional Packs provides a complete Kitset.

Optional Hardware Pack includes:

• 1x Right Angle Male DIN41612 364 Keyed Bus Connector
• 2x M2.5 Stainless Steel Bolt 10mm (2 required for Right Angle Connector)
• 2x M2.5 Stainless Steel Hexagonal Nut (for above Bolts)
• 4x M3 Nylon PCB Spacer 12mm
• 8x M3 Nylon Bolt 6mm (for Spacer mounting)
• 1x 3 pin PCB Header (JP1)
• 1x 2 pin Jumper Cap (for JP1)

Optional Component Pack includes:

• 1x AS6C4008 512KB SRAM DIP32 (U2)
• 2x 74HCT670 4x4 Register File DIP16 (U5,U6)
• 1x 74HCT74 D Flip-Flop DIP14 (U7)
• 1x 4K7 1/8W Resistor (R1)
• 1x Resistor Network 4K7 SIP5 (RN1)
• 1x Resistor Network 4K7 SIP9 (RN2)
• 1x 220nf Capacitor 5mm (C1)
• 6x 100nf Capacitor 5mm (C2,C3,C4,C5,C6,C7))

Optional IC Sockets Pack includes:

• 3x DIP32 IC Socket (for U2,U3,U4)
• 1x DIP20 IC Socket (for U1)
• 2x DIP16 IC Socket (for U5,U6)
• 1x DIP14 IC Socket (for U7)

Optional Rotary Coded Switch Pack includes:

• 1x 0-F Rotary Coded Switch 3:3 (SW1)

Optional 2nd AS6C4008 512KB SRAM Pack includes:

• 1x AS6C4008 512KB SRAM DIP32 (U4)

Optional Programmed ATF16V8 PLD Pack includes:

Either:

• 1x ATF16V8 PLD Chip (U1) Tested and Programmed for the first Card (0). Or:
• 1x ATF16V8 PLD Chip (U1) Tested and Programmed for a second Card (1).

Optional Programmed SST39SF020 FLASH ROM Pack includes:

• 1x SST39SF020 256KB FLASH ROM DIP32 (U2) Tested and Programmed with the example Bootloaders for simple 6809 48K/16K Memory Map (Bank 0), and advanced 6809 56K/8K Memory Map (Bank 1).

Banked Memory Expansion Card BOM

The following is a full Bill Of Materials (BOM) to allow fully assembling your Banked Memory Expansion Card.

Note that the PCB is supplied, and all components are available in the Optional Packs.

Also, some components are of course optional. For example the regular IC Sockets. Although I do recommend using IC Sockets throughout, for easy of trouble-shooting.

Default (PCB Only)

Optional Packs

Further Information

The Video linked below (to be added on Sat 7 November), provides a full presentation of the Banked Memory Expansion Card, as well as demonstrating the steps I took for assembly, and a walkthrough of both the PLD and the 6809 Assembly code examples.

Via the Documentation link (below) you'll also find follow-up videos, and other videos presenting different components of the MECB retro 8-bit computing project.

Your Banked Memory Expansion Card Kitset order is shipped in a robust cardboard carton with packing, for safe delivery via New Zealand International Air Parcel (see example shipping photo).

Note: Please visit the Documentation link (below) for more information on MECB, and for details of the various MECB Cards that have been design so far.

We pride ourselves with our "Next Business Day" Shipping Policy, and robust carton packaging. We also build to order, so if you order items with an "Assemble it for me" option selected, it may slightly delay shipping (while we build it for you).