The interrupt vectors are in ROM, so you cannot rewrite the vectors. However, there are vectors located at [0x7FC0 + level*4] which can be written to provide arbitrary handling for the interrupt.
PC-FX interrupts are level-triggered, so unless you clear the interrupt, the PC-FX will hang permanently.
Interrupt levels correspond to the devices like so:
| Interrupt level | Device |
|---|---|
| 15 | HuC6273 (Aurora) |
| 14 | HuC6270-B (7up) |
| 13 | HuC6272 (KING) |
| 12 | HuC6270-A (7up) |
| 11 | Pad |
| 10 | EX (?) |
| 9 | Timer |
| 8 | Reset |
| 0xE40 | Interrupt mask (R/W) |
|---|---|
| 0xE80 | Interrupt priority (R/W) |
| 0xEC0 | Interrupt priority (R/W) |
Mask for interrupt levels.
| Bits | Description |
|---|---|
| 0 | Interrupt Mask Level 15 |
| 1 | Interrupt Mask Level 14 |
| 2 | Interrupt Mask Level 13 |
| 3 | Interrupt Mask Level 12 |
| 4 | Interrupt Mask Level 11 |
| 5 | Interrupt Mask Level 10 |
| 6 | Interrupt Mask Level 9 |
| 7 | Interrupt Mask Level 8 |
Specify interrupt priorities for levels 12 ~ 15.
These priority levels correspond to the V810 interrupt levels on (INTV0-INTV3)
| Bits | Description |
|---|---|
| 0 ~ 2 | Interrupt level 15 priority (0 ~ 7) |
| 3 ~ 5 | Interrupt level 14 priority (0 ~ 7) |
| 6 ~ 8 | Interrupt level 13 priority (0 ~ 7) |
| 9 ~ 11 | Interrupt level 12 priority (0 ~ 7) |
Specify interrupt priorities for levels 8 ~ 11.
These priority levels correspond to the V810 interrupt levels on (INTV0-INTV3)
| Bits | Description |
|---|---|
| 0 ~ 2 | Interrupt level 11 priority (0 ~ 7) |
| 3 ~ 5 | Interrupt level 10 priority (0 ~ 7) |
| 6 ~ 8 | Interrupt level 9 priority (0 ~ 7) |
| 9 ~ 11 | Interrupt level 8 priority (0 ~ 7) |