v16.h

//The V16 Virtual Machine
//Licensed under the "BSD-2-Clause" License

#ifndef _V16_H
#define _V16_H

//Standard C Header Files
#include <stdint.h>
#include <stddef.h>

//V16 Macro Definitions
#define V16_MAXRAM      0x10000         //V16 Can address 128KiB of RAM (Address words!)
#define V16_REGISTERS   0x08            //V16 have 8 registers with direct access
#define V16_OADDR(o)    ((o >> 2) & 1)  //Operand mode ADDR bit
#define V16_OREG(o)     ((o >> 1) & 1)  //Operand mode REG bit
#define V16_OCONST(0)   (o & 1)         //Operand mode CONST bit

//Register aliases
//There are 8 registers and three of them are two-purposed
enum {
    REG_R0  = 0x00,

};

//Instruction structure
//Looks like PDP-11 instruction but with different purposes
//Instead of PDP11's 'B' bit and then 3-bit opcode, opcode there is a single 4-bit value
struct instr_s {
    uint8_t     opcode      : 4;    //Yes it is.

    uint8_t     dst_mode    : 3;    //DESTINATION:  Operand mode
    uint8_t     dst_reg     : 3;    //DESTINATION:  Register
    uint8_t     src_mode    : 3;    //SOURCE:       Operand mode
    uint8_t     src_reg     : 3;    //SOURCE:       Register

    uint16_t    dst_const;          //DESTINATION:  Optional constant
    uint16_t    src_const;          //SOURCE:       Optional constant
};
typedef struct instr_s instr_t;

//VM Structure
struct vm_s {
    uint16_t    ram[V16_MAXRAM];
    uint16_t    reg[V16_REGISTERS];
    int         status;
};
typedef struct vm_s vm_t;

//VM Structure/Functions
vm_t *      v16_delete(void);                                   //Create new VM
void        v16_delete(vm_t *vm);                               //Delete existing VM
uint16_t    v16_get_word(vm_t *vm);                             //Get word at (R7/IP)++
void        v16_start_at(vm_t *vm, uint16_t at);                //Start at address
void        v16_set_value(vm_t *vm, instr_t *i, uint16_t v);    //Set value to dst operand
void        v16_parse_instr(vm_t *vm, instr_t *i);              //Parse instruction

#endif