rosco_m68k bus board

The bus board is the backplane of a rosco_m68k system: five identical slots, wired pin for pin, that carry the full 64-pin rosco_m68k expansion bus. The main board and expansion cards plug onto them and share one bus and one supply.

• Slots: five, each a 2×32 header with the expansion bus plus a 2×8 header with 16 spare lines (EXT1 to EXT16), joined slot to slot
• Power: from USB, from a regulated 5 V DC supply, or from 9–12 V DC through the on-board L7805 regulator, chosen with one jumper cap
• Inputs: micro USB, a centre-positive DC jack and a 2-way screw terminal, with a power switch and a power LED
• Board: 160 × 116 mm, through-hole parts only

Build it#

The build guide takes you through four soldering stages with a board map for each, then shows how to pick the supply jumper and check the voltage before any card goes in. It is also available as a PDF to print.

Reference#

• Power and jumpers: which supply to use, what JP4–JP6 do, and how much current each option can give
• Bus signals: every signal on the slots, for card designers and fault finding
• FAQ: short answers to the most common questions

The rosco_m68k bus board is open-source hardware by Ross Bamford and contributors, released under the CERN Open Hardware Licence.