kara-abdelaziz/sep-cpu

SEP, for Simple Enough Processor, is an elaborated from scratch simulated (on Logisim) educational CPU

SEP-CPU

SEP (for Simple Enough Processor) is a simplistic academic processor to construct step-by-step by the student, it is an 8-bits CPU using an academic logic simulator called Logisim, supporting major real-world CPUs capabilities, like multiple programmable registers, multiple addressing modes, shift instruction, comparison and logic instructions, multiple branch and jump instructions the stack and subroutine mechanisms, flags indicators, input/output mechanism, a proper assembler... etc. The processor would comprise 21 instructions and 4 addressing modes, with the capability using the flexible control unit sequencer, to easily add more customizable instructions architectures.

How to run/execute a program

To run a program on SEP you have to follow these steps :

• STEP 1 : Download Logisim to your local machine, a jar version will work for any operating system.
• STEP 2 : Download this repository, and locate the programs with the extension .RAM, they are found in the directory /programs.
• STEP 3 : Open with Logisim the circuit SEP architecture.circ in the root directory.
• STEP 4 : Under Logisim, right-click upon the RAM circuit and click load image menu. Choose one program (.RAM files not .ASM) to load for the architecture.
• STEP 5 : Finally, you have to launch under Logisim the simulation. Some programs require an input from the user, which could be done using the SEP keyboard (it is a binary 8-bits keyboard).
• STEP 6 : Simulation could be done step-by-step or continuously, the result will be displayed on the seven segment display.

How to assemble a program

To assemble your own assembly program, you have to write the program with SEP assembly language, you can get some inspiration from programs with the extension .ASM within /programs directory. Then you have to compile them online using CustomAsm. The output format should be Logisim 8-bits. And you have to add the header SEP-CPU definition before the compilation, you can copy-paste it from other programs .ASM (/programs directory). The output is usually saved under .RAM file extension.