Note: The 1MB ROM Expansion Card is supplied in Kitset form only (assembly required). The base price is for the double-sided silkscreened ROM Expansion Card PCB ONLY. The Optional Packs provide all of the components for a full 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 with 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.

What is the 1MB ROM Expansion Card

The 1MB ROM Expansion Card provides up to 1MB of FLASH ROM via two SST39SF040 512KB FLASH ROM chips.

Configurable for either manual 64K Bank Select of one of 16 possible 64KB Banks for your 8-bit CPU Card, or as a full linear 1MB address space via the Bus extended A16 - A19 addressing. You can also configure the actual ROM space allocated in your Memory Map via the PLD (as with all MECB Cards).

Of course, you only need to populate the one ot two ROM chips, depending on whether you want 512MB (or eight switchable 64KB Banks), or the full 1MB (for sixteen switchable 64KB Banks).

What You Get

To satisfy different people's needs, I've split the 1MB ROM Expansion Card Kitset into Optional add-on Packs.

Firstly, note that the base price is for the double-sided silkscreened 1MB ROM Expansion Card PCB Only.

Then, you can add the optional Packs that might be helpful to you. Adding all of 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
• 1x 2-pin Jumper Cap

Optional Rotary Coded Switch Pack includes:

• 16-position (0-F) Rotary Coded Switch 3:3 pinout. Note that you can use a 4-way DIP Switch instead, but the Rotary Coded Switch is significantly easier for quick bank selection.

Optional Programmed ATF16V8 PLD Pack includes:

• An ATF16V8 PLD Chip Tested and Programmed as per Part 2 of the linked Video (i.e. Manually Switched ROM Banks with the top 16KB of the 64K address space allocated to the ROM).

Optional Programmed SST39SF040 FLASH ROM Pack includes:

• An SST39SF040 FLASH ROM Chip Tested and Programmed as per Part 2 of the linked video (i.e. ASSIST09 in Bank 0, and Extended BASIC in Bank 1, configured for 16KB ROM allocation to match above PLD, and I/O page $C0).

Optional Blank SST39SF040 FLASH ROM Pack includes:

• A blank SST39SF040 FLASH ROM Chip, either as a second ROM chip, or if you just require a blank chip for your own programming.

Optional Component Pack includes:

• 1x 74HCT257 Quad 2-Input Multiplexer DIP16 (U4)
• 1x 74HCT04 Hex Inverter DIP14 (U5)
• 1x Resistor Network 10K SIP9 (RN1)
• 4x 0.1µf Capacitor 5mm (C1,C2,C3,C4)

Optional IC Sockets Pack includes:

• 2x DIP32 IC Socket Round Pin (for U2,U3)
• 1x DIP20 IC Socket Round Pin (for U1)
• 1x DIP16 IC Socket Round Pin (for U4)
• 1x DIP14 IC Socket Round Pin (for U5)

1MB ROM Expansion Card BOM

The following is a full Bill Of Materials (BOM) to allow fully assembling your 1MB ROM Expansion Card.

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

Some components are of course optional. For example the IC Sockets, although I do highly recommend IC Sockets are used for all ICs. Also, note that you only need to install the one ROM chip (if only 512KB is required).

Default (PCB Only)

Optional Packs

Further Information

The Video linked below provides a Part 1 presentation, which includes assembly, of this 1MB ROM Expansion Card. A Part 2 video is also available, which includes ROM and PLD programming and the testing of the Card.

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

Your 1MB ROM 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.