I don't know how to name proprly my projects anymore.
Anyways, this is a CPU I made in Logisim-Evolution for fun. It uses 48-bit wide instructions, and 16-bit addressing.
The Instructions look like this:
IIIIIIIIIIIIIIIIAAAAAAAAAAAAAAAABBBBBBBBBBBBBBBB
The first part is a 16-bit opcode, and the two other ones are 16-bit arguments that are interpreted differently from one instruction to another, but usually A represents an input/source address and B and output/destination address.
The memory is split in two, the first 8 bytes are dedicated to registers and expansion ports and the rest is RAM (making the 8 first bytes of RAM unusable)
00: REG A01: REG B (ALU Mode)02: REG C (ALU A)03: REG D (ALU B)04: REG E (ALU Q)05: REG F (Port 1)06: REG G (Port 2)07: REG H (Port 3)
The ALU modes are described in ALU Modes.
Writing machine code is a bit borring so I made a small compiler to turn some assembly into machine code that can then be ran on the EPU itself.
In order to do that, I have provided a few examples in examples/ as well as a reference program.
To compile them, simply run main.js YOUR_PROGRAM. This will generate a src.bin file, which can then be imported in the ROM component on the rightmost side.
You might see a lot of random stuff in the console, but don't worry about that.
I am also working on errors, as well as macros, functions, a call stack and more, but this is not the project I'm currently working on the most, so when I come back to it I'll make sure to do that.
The communication with the ALU can be done though 4 ports, 3 inputs and 1 output,
The ALU can do 16 different operations:
| ALU Mode | Variable | Description |
|---|---|---|
00 |
alu_sum |
A + B |
01 |
alu_div |
A / B |
02 |
alu_mod |
A % B |
03 |
alu_div |
A - B |
04 |
alu_mod |
A * B |
05 |
alu_and |
A & B |
06 |
alu_or |
A | B |
07 |
alu_xor |
A ^ B |
08 |
alu_nand |
~( A & B ) |
09 |
alu_nor |
~( A | B ) |
0A |
alu_nxor |
~( A ^ B ) |
0B |
alu_shl |
A << B |
0C |
alu_shr |
A >> B |
0D |
alu_rol |
A << B (rotation) |
0E |
alu_ror |
A >> B (rotation) |
0F |
alu_rng |
returns a pseudo-random number |
For convenience, there are a few variables related to the ALU, like alu_mode, which is the register for the ALU mode, alu_a and alu_b for the two arguments, alu_q for the ALU output, and all the modes as described above.
Special components can be linked to addresses 7, 6 and 5.
On this build, they are all occupied by the TTY Screen, the RGB Screen and the Keyboard.
The components can be directly connected to the cata lines rather than relying on a register, which is way more practical for the keyboard for example.