Tiny Instruction Set Computer

This is a for-fun implementation of a relatively simple micro-architecture, with an assembler to program the simulated implementation in Logisim.

My goal with this project is to aim for an instruction set architecture that is focused on minimal scale. I've written about the first ressurection of this project on my blog before and I am sporatically finding ways to explore the original idea of "minimal scale" through modifications and continuation of work contained within this repository.

Want to play with it too?

The default program loaded in the ExampleConfigurationROM circuit is the ExamplePrograms/expanded_terminal.tac program. The program is an interactive demo which processes text input from the keyboard component and echoes the text out to the TTY component. The 32 characters are buffered and compared to existing command strings with routines to execute per each command string.

Compiling the assembler

To compile the assembler, I recommend using GCC:

$ gcc tisc.c -o tisc

Using the assembler

Once the assembler is compiled, you can assemble TISC assembly code like so:

$ ./tisc <input file> <output file>

If the assembler found no errors in the code, the output file will contain the program that is ready to load into the Logisim circuit.

A successful output will appear like this:

$ ./tisasm ExamplePrograms/fibb_test.tac out
Assembling tac file: 'ExamplePrograms/fibb_test.tac' TISC v2.4
label line  addr:out>op         args
      0003  0000:43| li  0xFD  
            0001:fd|
      0004  0002:9f| sp  GRA  
      0006  0003:c2| one  GRC  
loop  0008  0004:ab| sb  GRB  
      0010  0005:c9| xor  GRB GRC 
      0011  0006:cd| xor  GRC GRC 
      0012  0007:c9| xor  GRB GRC 
      0014  0008:ba| op  GRB GRC GRB
      0016  0009:fb| cmp  GRB GRC 
      0017  000a:83| jmp  loop  
            000b:04|
      0019  000c:ab| sb  GRB  
end   0020  000d:83| jmp  end  
            000e:0d|
Finished assembling tac file: 'ExamplePrograms/fibb_test.tac', program size: 15 bytes

Loading a program

The provided example application in the circuit ExampleConfigurationROM is a configuration with memory-mapped I/O. The I/O at memory address 0xFF is a ROM that acts as the program memory. Left-clicking on the component and selecting 'Load Image' will allow you to load memory images generated by the assembler.