HomeTechnologyComputingThe MikroLeo Is a Four-Bit "Didactic Microcomputer" That Aims to Teach Core...

The MikroLeo Is a Four-Bit “Didactic Microcomputer” That Aims to Teach Core Computing Concepts

Brazilian electrical engineer Edson Junior Acordi has created a design for a “didactic microcomputer” called the MikroLeo, designed around a simplified four-bit instruction set architecture for the purpose of teaching core computing concepts.

“[MikroLeo] is aimed at students, enthusiasts, hackers, professors and anyone who wants to understand or improve electronics and learn how a simple computer works,” explains Acordi about the project, which was developed in collaboration with Matheus Fernando Tasso and Carlos Daniel de Souza Nunes “In addition, it is also an attempt to salvage the story of the early development of integrated circuits and computers on a single chip, to demonstrate the capabilities that these machines had at the time.”

The MikroLeo design, which can be built on a series of interconnected breadboards or on a dual-layer PCB with purely through-hole components, implements a custom four-bit processor with up to 4KB RAM, 4KB ROM, four input and output ports each with a total of 16 inputs and 16 outputs, and avoids the relative complexity of modern machines by being built entirely without microprocessors, microcontrollers or microcode.

The machine’s instruction set architecture is based on the Harvard architecture with a reduced instruction set of only 20 instructions, although Acordi notes that changing the addressing mode or modifier bits allows for a total of 64 possible instruction combinations. The design also includes four registers – an accumulator, two general purpose registers and one special purpose register, all four bits wide – and two flags, the carrier flag and the null flag.

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The PCB design has been completed and the computer is now undergoing final testing. (: Edson Junior Acordi)

Other features of the design include the ability to run step-by-step, with a clock speed of 3 MHz and a precise time base, or with an adjustable clock speed, indirect addressing for subroutine support, and the ability to program directly using physical input switches or via connection to an Arduino or Espressif ESP32 microcontroller board.

Design files and source code for the MikroLeo are available on the project’s GitHub repository under the CERN Open Hardware License Version 2 Strongly Reciprocal and the GNU General Public License 3, respectively.

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