Simple CPU model written in 60 lines of code

CPU60 is a simple CPU model written in 60 lines of C code.

It supports 8 registers and several simple instructions: mov, add, addi, sub, subi, and, andi, or, ori instructions. Following each instruction is the CPU register dump. By default input is read from the standard input.

Flag -r might be passed to simulate the proper reset of the CPU. Upon reset, all registers are filled with 0's. Without -r, the values of the registers are undefined, and your program instructions can't depend on register's content.

How to build

To build:

make

How to run

Either manually:

% ./cpu60
reg0=a7   reg1=f1   reg2=d9   reg3=2a   reg4=82   reg5=c8   reg6=d8   reg7=fe
sub r0,r0,r0
reg0=00   reg1=f1   reg2=d9   reg3=2a   reg4=82   reg5=c8   reg6=d8   reg7=fe sub r0,r0,r0
sub r1,r1,r1
reg0=00   reg1=00   reg2=d9   reg3=2a   reg4=82   reg5=c8   reg6=d8   reg7=fe sub r1,r1,r1
ori r0,r0,1
reg0=01   reg1=00   reg2=d9   reg3=2a   reg4=82   reg5=c8   reg6=d8   reg7=fe ori r0,r0,1
ori r1,r1,2
reg0=01   reg1=02   reg2=d9   reg3=2a   reg4=82   reg5=c8   reg6=d8   reg7=fe ori r1,r1,2
add r2,r0,r1
reg0=01   reg1=02   reg2=03   reg3=2a   reg4=82   reg5=c8   reg6=d8   reg7=fe add r2,r0,r1

Or from file:

% cpu60 < file

Where file can have any valid opcodes.

How to test

To unit test the model, hit:

make test

Author

• Wojciech Adam Koszek, [email protected]
• http://www.koszek.com