cComputer (WIP)

cComputer stands for Cryx's computer
This is an attempt to make a very basic CPU with its own assembly language and compiler without any prior important knowledge. This repository is more an experiment that anything else. Therefore it SHOULD NOT be used in any of your projects or even has a relevant example. Logisim Evolution will be used to create the different needed circuits for the CPU.

16-bits CPU
40-bits Instructions wide

Display

64x64   Screen
15-bits Colors

Memory

Program:            ROM 512   x 40
General + Video:    RAM 64K   x 16 (0x0000 - 0x0020 reserved)
                                   (0xF000 - 0xFFFF video)

Instructions

Syntax

'#1234'  => decimal format
'#$ABCD' => hexadecimal format
'#%1011' => binary format

'xxxx:' => Create a label named xxxx

Register codes

R0: 0x0000
R1: 0x0001
R2: 0x0002
R3: 0x0003
R4: 0x0004
R5: 0x0005
R6: 0x0006
R7: 0x0007

Instructions set

- If a '=>' is visible, it means that the value will be stored into the
  concerned register.
- CMP and TST will store their value (1/0) into a flag.
- Pointers can be used for instructions with *R args, such as MOV and SET. 
  eg: MOV *R0 R1, will copy the content of the memory at address R0 into R1
  The usage of pointers will be ignored for CMP and TST

R=Register; A=Address; V=Value; L=Label; *=Pointer

8-bits      16-bits 16-bits
0xAB        0xABCD  0xABCD

0x00    NOP                     // Nothing
0x01    MOV *RAx *RAy           // Move Y to X
0x02    SET *RA  V              // Set value V

0x10    ADD Rx Ry => Rx=Rx+Ry   // Add
0x11    SUB Rx Ry => Rx=Rx-Ry   // Subtract
0x12    MUL Rx Ry => Rx=Rx*Ry   // Multiply
0x13    DIV Rx Ry => Rx=Rx/Ry   // Divide

0x14    NOT Rx    => Rx=!Rx     // NOT operator
0x15    AND Rx Ry => Rx=Rx&Ry   // AND operator
0x16    ORR Rx Ry => Rx=Rx|Ry   // OR operator
0x17    XOR Rx Ry => Rx=Rx^Ry   // XOR operator
0x18    ROL Rx Ry => Rx         // Left rotation of Ry bits
0x19    ROR Rx Ry => Rx         // Right rotation of Ry bits 

0x20    CMP Rx Ry               // Compare Rx to Ry
0x21    TST R                   // Test R

0x30    BEQ L                   // Go to label L if equal
0x31    BNE L                   // Go to label L if not equal
0x32    BLT L                   // Go to label L if lesser than
0x33    BGT L                   // Go to label L if bigger than
0x34    JMP L                   // Go to label L

0xF0    VID                     // Refresh video output

0xFF    HLT                     // Halt, stop the program

Usage

• Create a .casm file (examples are available in ./examples/)
• In ./compiler/ run make to create the compiler.
• Once the compiler is ready, run ./cryxc path_to_file.casm to compile the file, a file out.cout will be created. You can also run ./cryxc file.casm output_name to create instead the file output_name.cout in the desired directory.
• Run Logisim Evolution, load ./circuits/main.circ and load the .cout file into the ROM.
• Go into the Simulation tab to config the simulation and to run it.
• If you want to reset the simulation, you can click on the red button or press Ctrl-R.

The circuits

Main circuit

Subcircuit is_memaddr

Subcircuit is_pointer

Subcircuit get_addr_target

Subcircuit condition

Subcircuit ALU