Greetings FPGA lovers! Today’s post is about building your own mini computer using FPGA. The project has been inspired by the first SSEM, popularly called the Manchester baby. The project resembles its inspiration in certain aspects, but being a homemade CPU with minimal components and coding, the specs are not as formidable as the SSEM.
The author has used a standard FPGA Papilo one 500k board, an 8×8 LED strip and a set of switches. The system has been designed for a total RAM of 64 bits, and the LED strip shows the RAM configuration every time data is entered at a new address. Besides this, the author has also used a rechargeable battery, charging circuit, clipper circuit to avoid excess voltage and a number of peripheral ICs.
The coding followed for FPGA is based on simple VHDL (.vhd) and being an open source project, the author has shared all VHDL code here. The CPU is programmed directly using the address and data switches. A number of values can be stored just by setting the CPU on the User mode and entering data to the addresses of the 64 bit RAM.
The system also has an adjustable clock which helps while simulating and running the code in variable clock speeds. The author has successfully demonstrated through the video that the CPU can work as a Random number Generator (from 1 to 6) and a pendulum. Besides this the CPU can also be connected to external components like an array of LEDs for clarity of output.
Though the FPGA based C88 Homebrew CPU has limited RAM and storage capabilities, it is still a great start to create experimental modules and platforms using FPGA that can host a number of applications.