# Hardware vectors

Hardware vectors are a group of pointers that define how the SNES should handle certain interrupts within the ROM. Each vector is two bytes in size and point to instructions located in bank `$00`. The hardware vectors are grouped by the [two modes of the SNES](https://ersanio.gitbook.io/assembly-for-the-snes/processor-flags-and-registers/flags): "emulation mode" vectors and "native mode" vectors.

## Native mode vectors

These vectors come into play when the SNES runs in native mode (E=0).

| ROM address | Vector       | Additional notes                                                                                |
| ----------- | ------------ | ----------------------------------------------------------------------------------------------- |
| `$00:FFE0`  | Unused       |                                                                                                 |
| `$00:FFE2`  | Unused       |                                                                                                 |
| `$00:FFE4`  | COP vector   | Triggered by the [COP opcode](https://ersanio.gitbook.io/assembly-for-the-snes/deep-dives/misc) |
| `$00:FFE6`  | BRK vector   | Triggered by the [BRK opcode](https://ersanio.gitbook.io/assembly-for-the-snes/deep-dives/misc) |
| `$00:FFE8`  | ABORT vector | Unused by the SNES                                                                              |
| `$00:FFEA`  | NMI vector   | Triggered by the SNES V-Blank Interrupt                                                         |
| `$00:FFEC`  | Unused       |                                                                                                 |
| `$00:FFEE`  | IRQ vector   | Triggered by the SNES H/V-Timer or external interrupt                                           |

## Emulation mode vectors

These vectors come into play when the SNES runs in emulation mode (E=1).

| ROM address | Vector         | Additional notes                                                                                                                                          |
| ----------- | -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `$00:FFF0`  | Unused         |                                                                                                                                                           |
| `$00:FFF2`  | Unused         |                                                                                                                                                           |
| `$00:FFF4`  | COP vector     |                                                                                                                                                           |
| `$00:FFF6`  | Unused         |                                                                                                                                                           |
| `$00:FFF8`  | ABORT vector   | Unused by the SNES                                                                                                                                        |
| `$00:FFFA`  | NMI vector     |                                                                                                                                                           |
| `$00:FFFC`  | RESET vector   | Triggered by SNES soft/hard reset                                                                                                                         |
| `$00:FFFE`  | IRQ/BRK vector | It's possible to differentiate between the two using the [BRK flag](https://ersanio.gitbook.io/assembly-for-the-snes/processor-flags-and-registers/flags) |

## Example setup

Here's an example setup with the most commonly used vectors, which can be used in homebrew SNES ROMs. Note that the labels must be located in bank `$00` (which is located within the same bank as this setup).

```
ORG $00FFE0

; Native mode
dw $FFFF           ; Unused
dw $FFFF           ; Unused
dw $FFFF           ; COP
dw $FFFF           ; BRK
dw $FFFF           ; ABORT
dw NativeNMI       ; NMI
dw $FFFF           ; Unused
dw NativeIRQ       ; IRQ

; Emulation mode
dw $FFFF           ; Unused
dw $FFFF           ; Unused
dw $FFFF           ; COP
dw $FFFF           ; Unused
dw $FFFF           ; ABORT
dw $FFFF           ; NMI
dw Reset           ; RESET
dw $FFFF           ; IRQ/BRK
```

Because homebrew programmers generally want to run their program in native mode, all vectors in emulation mode, save for reset, have been ignored. Furthermore, nothing is done with the `BRK` and `COP` vectors as these are opcodes which generally are unused.