Note: The Motorola I/O Card is supplied in Kitset form only (assembly required). The base price is for the double-sided silkscreened Motorola I/O Card PCB ONLY. The Optional Packs together provide all that is required 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 the 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.

Motorola I/O + Sound Card

The Motorola I/O + Sound Card provides for a Motorola 6850 ACIA (Serial), a Motorola 6840 PTM (Timer), a Motorola 6821 PIA (GPIO), and also a SN76489 Complex Sound Generator (connected via Port B of the PIA).

Of course, you only need to populate the I/O chips that you require for your system. e.g. If you don't want sound, then don't install a SN76489 chip, which completely frees up Port B of the PIA for other uses. Likewise, if you only want a serial interface, just install a MC6850.

All I/O interface pins are exposed via the included board connectors.

What You Get

To satisfy different people's needs, I've split the Motorola I/O Card Kitset into Optional add-on Packs.

Firstly, note that the base price is for the double-sided silkscreened Motorola I/O Card PCB Only.

Then, you can add the Optional Packs that might be helpful to you. Selecting ALL Optional Packs will provide you with a Complete Kitset of parts.

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 2 pin PCB Header
• 1x 3 pin PCB Header
• 1x 2 pin Jumper Cap
• 1x 6 pin PCB Header Right-Angle
• 1x IDC Header 2x6 pin Straight
• 1x IDC Header 2x12 pin Right-Angle
• 1x 3.5mm Phone Connector Audio Jack PCB Mount
• 1x 4-way DIP Switch DIP8

Optional Programmed ATF16V8 PLD Pack includes:

• An ATF16V8 PLD Chip Tested and Programmed as per the linked Video (i.e. PTM $00-$07, ACIA $08-$0F, PIA $10-$17 I/O Address ranges).

Optional Discrete Components Pack includes:

• 1x Crystal Oscillator 4.9152Mhz DIP8
• 6x 0.1µf Capacitor 5mm
• 1x 47µf Radial Capacitor
• 2x 3K3 Resistor 0.125W

Optional Semiconductor Pack includes:

• 1x VN10KN or 2N7000 N-Channel MOSFET TO92
• 1x 74HCT393 Dual 4-bit binary ripple counter DIP14
• 1x Pre-tested MC68B50 ACIA DIP24 (2MHz)
• 1x Pre-tested MC68B40 PTM DIP28 (2MHz)
• 1x Pre-tested MC68B21 PIA DIP40 (2MHz)
• 1x Pre-tested SN76489AN Sound Generator DIP16

Optional IC Socket Pack includes:

• 1x DIP40 IC Socket (machined pin)
• 1x DIP28 IC Socket (machined pin)
• 1x DIP24 IC Socket (machined pin)
• 1x DIP16 IC Socket (machined pin)
• 1x DIP14 IC Socket (machined pin)
• 1x DIP8 IC Socket (machined pin)

Motorola I/O Card BOM

The following is a full Bill Of Materials (BOM) to allow fully assembling your Motorola I/O Card.

Note that the PCB is supplied, and all components are available via the Optional Packs. This includes pre-tested retro semiconductors.

Some components are of course optional. For example the IC Sockets, although I do highly recommend IC Sockets are used. Also, note that you only need to install the I/O chips (MC6840 PTM, MC6850 ACIA, MC6821 PIA, SN76489 Sound), that you are wanting to actually use.

The Video linked below provides a presentation of this Motorola I/O + Sound Card, as well as demonstrating the steps I took for assembly and testing.

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.

Default (PCB Only)

Optional Packs

Your Motorola I/O Card Kitset order is shipped in a robust cardboard carton with packing, for safe delivery via New Zealand International Tracked 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.