#+OPTIONS: toc:nil num:nil <:nil \n:nil ::nil timestamp:nil *:nil ':nil
#+HTML_HEAD: <link rel="stylesheet" type="text/css" href="style.css"/>
#+EXPORT_FILE_NAME: index.html
#+title: ocpu

*  GRU ocpu - yet another cpu design
** Features
   - little endian
   - 8-bit (maybe will be changed in future)
** Registers
   
   |----------+----------+-----------------|
   | Register | Category | Description     |
   |----------+----------+-----------------|
   | A        | General  | 0x0A            |
   |----------+----------+-----------------|
   | B        | General  | 0x0B            |
   |----------+----------+-----------------|
   | C        | General  | 0x0C            |
   |----------+----------+-----------------|
   | D        |          | 0x0D            |
   |----------+----------+-----------------|
   | E        |          | 0x0E            |
   |----------+----------+-----------------|
   | F        |          | 0x0F            |
   |----------+----------+-----------------|
   | PC       | Pointer  | Program Counter |
   |----------+----------+-----------------|
   | SP       | Poiner   | Stack Pointer   |
   |----------+----------+-----------------|
   | ZF       | Flag     | Zero Flag       |
   |----------+----------+-----------------|
   | NF       | Flag     | Negative Flag   |
   |----------+----------+-----------------|
   | CF       | Flag     | Carry Flag      |
   |          |          |                 |
   |----------+----------+-----------------|
   | OF       | Flag     | Overflow Flag   |

** Instuctions
   
   |--------------+--------+-------------------------------------------|
   | Instructions | Opcode | Description                               |
   |--------------+--------+-------------------------------------------|
   | MOV          |   0x01 | Place value to register.                  |
   |              |        | Takes 2 bytes as arguments:               |
   |              |        | 1 - Opcode of register                    |
   |              |        | 2 - Value                                 |
   |              |        |                                           |
   |--------------+--------+-------------------------------------------|
   | ADD          |   0x10 |                                           |
   |--------------+--------+-------------------------------------------|
   | ADC          |   0x11 |                                           |
   |--------------+--------+-------------------------------------------|
   | SUB          |   0x12 |                                           |
   |--------------+--------+-------------------------------------------|
   | MUL          |   0x13 |                                           |
   |--------------+--------+-------------------------------------------|
   | DIV          |   0x14 |                                           |
   |--------------+--------+-------------------------------------------|
   | INC          |   0x15 | Increment                                 |
   |--------------+--------+-------------------------------------------|
   | DEC          |   0x16 | Decrement                                 |
   |--------------+--------+-------------------------------------------|
   | AND          |   0x20 |                                           |
   |--------------+--------+-------------------------------------------|
   | OR           |   0x21 |                                           |
   |--------------+--------+-------------------------------------------|
   | NOR          |   0x22 |                                           |
   |--------------+--------+-------------------------------------------|
   | XOR          |   0x23 |                                           |
   |--------------+--------+-------------------------------------------|
   | NAND         |   0x24 |                                           |
   |--------------+--------+-------------------------------------------|
   | CMP          |   0x25 |                                           |
   |--------------+--------+-------------------------------------------|
   | PUSH         |   0x30 |                                           |
   |--------------+--------+-------------------------------------------|
   | POP          |   0x31 |                                           |
   |--------------+--------+-------------------------------------------|
   | JMP          |   0x40 |                                           |
   |--------------+--------+-------------------------------------------|
   | JSR          |   0x41 | Jump to subroutine                        |
   |--------------+--------+-------------------------------------------|
   | JC           |   0x42 | Jump with carry                           |
   |--------------+--------+-------------------------------------------|
   | JNC          |   0x43 | Jump without carry                        |
   |--------------+--------+-------------------------------------------|
   | JZ           |   0x44 | Jump if zero                              |
   |--------------+--------+-------------------------------------------|
   | JNZ          |   0x45 | Jump if non-zero                          |
   |--------------+--------+-------------------------------------------|
   | RTS          |   0x42 | Return from subroutine                    |
   |--------------+--------+-------------------------------------------|
   | INB          |   0x50 | Copies value from I/O port to destination |
   |--------------+--------+-------------------------------------------|
   | OUTB         |   0x51 | Copies value from operand to I/O port     |
   |--------------+--------+-------------------------------------------|
   | NOP          |   0x90 | No operation                              |


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

0x90 - NOP


TODO: add interrupts

TODO: add HLT

TODO: make instructions for memory use