The smallest DIL40 8085-based computer

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DIL40 footprint, 32 KiB RAM, 64 KiB ISP Flash, console via USB VCOM, full hardware monitor.


  • footprint: 80C85 DIL40 socket (width: + 50 mils)
  • hardware monitor with single-stepping, disassembly, memory editing and drag-and-drop HEX file loading
  • 32 KiB RAM, 64 KiB ISP Flash
  • terminal (console) interface with interrupt capability
  • timer with interrupt and single LED controlled via an output port
  • SOD output connected to a LED, SID input controlled by a button or monitor command
  • Power supply, h/w monitor communication and target computer terminal via USB double VCOM device
  • whole computer logic implemented in STM32L412C microcontroller placed under the CPU

Software needed on PC side: a terminal emulator program (TeraTerm 4.101 or newer is recommended).


Revised schematic w/ corrected LED control by SOD output.

Portable Network Graphics (PNG) - 47.87 kB - 02/20/2019 at 19:24


  • 1 × 80C85
  • 1 × STM32L412

  • It's stable now

    gbm02/19/2019 at 11:49 0 comments

    Fixed the timing problem related to clock generation, looks like the machine works stable now and TinyBASIC doesn't break..

  • Mostly working

    gbm02/06/2019 at 19:21 0 comments

    The SDC_85 runs TinyBASIC for 15 minutes, then the BASIC  goes wild. Looks like some memory corruption - needs sorting out.

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