This structure will be used to represent the state of the Central Processing Unit (CPU) of our emulator. This Virtual CPU emulates a "MOS Technology 6502". More...
#include <cpu.h>
Public Attributes | |
| address | program_counter |
| An address pointing to the next instruction to be executed. | |
| data | stack_pointer |
| A register that holds the 8 lower bytes of the address 0x11??. | |
| data | cache |
| A 8 bit reserved space that I use for some operations. | |
| data | accumulator |
| A 8 bit register used to perform operations. | |
| data | register_x |
| A 8 bit register. Commonly used to hold offset and counters. | |
| data | register_y |
| A 8 bit register. Commonly used to hold offset and counters. | |
| data | flags |
| NVPBDIZC. | |
| unsigned char | cycle_counter |
| The cycle counter. The counter is decremented every step. | |
| memory | mem |
| A direct access to the Emulator Memory. | |
Detailed Description
This structure will be used to represent the state of the Central Processing Unit (CPU) of our emulator. This Virtual CPU emulates a "MOS Technology 6502".
Here's some informations about this CPU:
- It is a 8-bits register with a 16-bits addressing mode.
- There is 3 work registers: Accumulator, Register Index X, Register Index Y
- There is a Register that holds the processor intern flags. Here's its layout:
- N: Negative. Set if the result of an operation is negative.
- V: Overflow. Set if an arithmetic operation between two numbers cause and integer overflow (For instance: 64+64=-128).
- P: Unused on the NES, I'll use it as a "paused" state.
- B: Break. Set if the BRK instruction is encountered or when an interrupt is raised.
- D: Decimal. When set, the processor will obey the rule of BCD for add and sub.
- I: Interrupt Disable. When set, the processor will not respond to any interrupt.
- Z: Zero. Set if the result of the last operation is zero.
- C: Carry. Set if the last operation caused an overflow from bit 7 or an underflow from bit 0
Member Data Documentation
◆ accumulator
| data CPU::accumulator |
A 8 bit register used to perform operations.
Definition at line 31 of file cpu.h.
Referenced by init_cpu(), main(), print_cpu_state(), and printw_cpu_state().
◆ cache
| data CPU::cache |
A 8 bit reserved space that I use for some operations.
Definition at line 30 of file cpu.h.
Referenced by init_cpu().
◆ cycle_counter
| unsigned char CPU::cycle_counter |
The cycle counter. The counter is decremented every step.
Definition at line 37 of file cpu.h.
Referenced by init_cpu(), and step_cpu().
◆ flags
| data CPU::flags |
NVPBDIZC.
Definition at line 35 of file cpu.h.
Referenced by init_cpu(), main(), and print_cpu_state().
◆ mem
| memory CPU::mem |
A direct access to the Emulator Memory.
Definition at line 39 of file cpu.h.
Referenced by execute_instruction(), free_cpu(), get_next_instruction(), init_cpu(), main(), print_stack_state(), start_cpu(), and step_cpu().
◆ program_counter
| address CPU::program_counter |
An address pointing to the next instruction to be executed.
Definition at line 28 of file cpu.h.
Referenced by execute_instruction(), get_next_instruction(), init_cpu(), print_cpu_state(), printw_cpu_state(), start_cpu(), and step_cpu().
◆ register_x
| data CPU::register_x |
A 8 bit register. Commonly used to hold offset and counters.
Definition at line 32 of file cpu.h.
Referenced by execute_instruction(), get_next_instruction(), init_cpu(), main(), print_cpu_state(), and printw_cpu_state().
◆ register_y
| data CPU::register_y |
A 8 bit register. Commonly used to hold offset and counters.
Definition at line 33 of file cpu.h.
Referenced by execute_instruction(), get_next_instruction(), init_cpu(), main(), print_cpu_state(), and printw_cpu_state().
◆ stack_pointer
| data CPU::stack_pointer |
A register that holds the 8 lower bytes of the address 0x11??.
Definition at line 29 of file cpu.h.
Referenced by init_cpu(), main(), print_cpu_state(), print_stack_state(), and printw_cpu_state().
The documentation for this struct was generated from the following file:
- include/core/cpu.h
