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*  GRU ocpu - yet another cpu design
** Features
   - little endian
   - 16-bit
** Registers
   
   |----------+----------+-------------------------|
   | Register | Category | Description             |
   |----------+----------+-------------------------|
   | AL       | General  | 0xA0, 8-bit             |
   |----------+----------+-------------------------|
   | AH       | General  | 0xA1, 8-bit             |
   |----------+----------+-------------------------|
   | A        | General  | 0x0A, 16-bit            |
   |----------+----------+-------------------------|
   | BL       | General  | 0xB0, 8-bit             |
   |----------+----------+-------------------------|
   | BH       | General  | 0xB1, 8-bit             |
   |----------+----------+-------------------------|
   | B        | General  | 0x0B, 16-bit            |
   |----------+----------+-------------------------|
   | CL       | General  | 0xC0, 8-bit             |
   |----------+----------+-------------------------|
   | CH       | General  | 0xC1, 8-bit             |
   |----------+----------+-------------------------|
   | C        | General  | 0x0C, 16-bit            |
   |----------+----------+-------------------------|
   | DL       |          | 0xD0, 8-bit             |
   |----------+----------+-------------------------|
   | DH       |          | 0xD1, 8-bit             |
   |----------+----------+-------------------------|
   | D        |          | 0x0D, 16-bit            |
   |----------+----------+-------------------------|
   | EL       |          | 0xE0, 8-bit             |
   |----------+----------+-------------------------|
   | EH       |          | 0xE1, 8-bit             |
   |----------+----------+-------------------------|
   | E        |          | 0x0E, 16-bit            |
   |----------+----------+-------------------------|
   | FL       |          | 0xF0, 8-bit             |
   |----------+----------+-------------------------|
   | FH       |          | 0xF1, 8-bit             |
   |----------+----------+-------------------------|
   | F        |          | 0x0F, 16-bit            |
   |----------+----------+-------------------------|
   | PC       | Pointer  | Program Counter, 16-bit |
   |----------+----------+-------------------------|
   | SP       | Pointer  | Stack Pointer, 16-bit   |
   |----------+----------+-------------------------|
   | ZF       | Flag     | Zero Flag               |
   |----------+----------+-------------------------|
   | NF       | Flag     | Negative Flag           |
   |----------+----------+-------------------------|
   | CF       | Flag     | Carry Flag              |
   |          |          |                         |
   |----------+----------+-------------------------|
   | OF       | Flag     | Overflow Flag           |

** Instuctions
   
   |-----------------+--------+-------------------------------------------|
   | Instructions    | Opcode | Description                               |
   |-----------------+--------+-------------------------------------------|
   | MOV reg, imm16  |   0x01 | Place value to register.                  |
   | MOV reg, reg    |   0xA1 | Takes 2 bytes as arguments:               |
   |                 |        | 1 - Opcode of register                    |
   |                 |        | 2 - Value or register                     |
   |                 |        |                                           |
   |-----------------+--------+-------------------------------------------|
   | ADD reg, imm16  |   0x10 | Add                                       |
   | ADD reg, reg    |   0xB0 |                                           |
   |-----------------+--------+-------------------------------------------|
   | ADC reg, imm16  |   0x11 | Add with carry                            |
   | ADC reg, reg    |   0xB1 |                                           |
   |-----------------+--------+-------------------------------------------|
   | SUB reg, imm16  |   0x12 | Subtract                                  |
   | SUB reg, reg    |   0xB2 |                                           |
   |-----------------+--------+-------------------------------------------|
   | MUL reg, imm16  |   0x13 | Multiply                                  |
   | MUL reg, reg    |   0xB3 |                                           |
   |-----------------+--------+-------------------------------------------|
   | DIV reg, imm16  |   0x14 | Divide                                    |
   | DIV reg, reg    |   0xB4 |                                           |
   |-----------------+--------+-------------------------------------------|
   | INC reg         |   0x15 | Increment                                 |
   |                 |        |                                           |
   |-----------------+--------+-------------------------------------------|
   | DEC reg         |   0x16 | Decrement                                 |
   |-----------------+--------+-------------------------------------------|
   | NOT reg         |   0x20 | Logical NOT                               |
   |-----------------+--------+-------------------------------------------|
   | AND reg, imm16  |   0x21 | Logical AND                               |
   | AND reg, reg    |   0xC1 |                                           |
   |-----------------+--------+-------------------------------------------|
   | OR reg, imm16   |   0x22 | Logical OR                                |
   | OR reg, reg     |   0xC2 |                                           |
   |-----------------+--------+-------------------------------------------|
   | NOR reg, imm16  |   0x23 | Logical NOR                               |
   | NOR reg, reg    |   0xC3 |                                           |
   |-----------------+--------+-------------------------------------------|
   | XOR reg, imm16  |   0x24 | Logical XOR                               |
   | XOR reg, reg    |   0xC4 |                                           |
   |-----------------+--------+-------------------------------------------|
   | NAND reg, imm16 |   0x25 | Logical NAND                              |
   | NAND reg, reg   |   0xC5 |                                           |
   |-----------------+--------+-------------------------------------------|
   | CMP reg, imm16  |   0x26 | Compare                                   |
   | CMP reg, reg    |   0xC6 |                                           |
   |-----------------+--------+-------------------------------------------|
   | PUSH imm16      |   0x30 | Push to stack                             |
   |-----------------+--------+-------------------------------------------|
   | POP             |   0x31 | Pop to stack                              |
   |-----------------+--------+-------------------------------------------|
   | JMP imm16       |   0x40 | Jump                                      |
   |-----------------+--------+-------------------------------------------|
   | JSR imm16       |   0x41 | Jump to subroutine                        |
   |-----------------+--------+-------------------------------------------|
   | JC imm16        |   0x42 | Jump with carry                           |
   |-----------------+--------+-------------------------------------------|
   | JNC imm16       |   0x43 | Jump without carry                        |
   |-----------------+--------+-------------------------------------------|
   | JZ imm16        |   0x44 | Jump if zero                              |
   |-----------------+--------+-------------------------------------------|
   | JNZ imm16       |   0x45 | Jump if non-zero                          |
   |-----------------+--------+-------------------------------------------|
   | JE imm16        |   0x46 | Jump if equal                             |
   |-----------------+--------+-------------------------------------------|
   | JL imm16        |   0x47 | Jump if lower                             |
   |-----------------+--------+-------------------------------------------|
   | JH imm16        |   0x48 | Jump if higher                            |
   |-----------------+--------+-------------------------------------------|
   | RTS             |   0x49 | Return from subroutine                    |
   |-----------------+--------+-------------------------------------------|
   | INB imm16       |   0x50 | Copies value from I/O port to destination |
   |-----------------+--------+-------------------------------------------|
   | OUTB imm16      |   0x51 | Copies value from operand to I/O port     |
   |-----------------+--------+-------------------------------------------|
   | NOP             |   0x90 | No operation                              |
   |-----------------+--------+-------------------------------------------|
   | SEC             |   0x61 | Set carry flag                            |
   |-----------------+--------+-------------------------------------------|
   | CLC             |   0x62 | Clear carry flag                          |


0x0* - MOV instructions (maybe it will for LDA or something)

0x1* - Arithmetic (ADD, SUB and others)

0x2* - Logic (AND, OR and others)

0x3* - Stack Operations (PUSH, POP)

0x4* - Jumps

0x5* - Ports Operations

0x6* - Flags Operations

0x90 - NOP


TODO: add interrupts

TODO: add HLT

TODO: add instructions for memory use

TODO: add more description