EXTI pending register
| PR0 | CPU Event mask on Event input x |
| PR1 | CPU Event mask on Event input x |
| PR2 | CPU Event mask on Event input x |
| PR3 | CPU Event mask on Event input x |
| PR4 | CPU Event mask on Event input x |
| PR5 | CPU Event mask on Event input x |
| PR6 | CPU Event mask on Event input x |
| PR7 | CPU Event mask on Event input x |
| PR8 | CPU Event mask on Event input x |
| PR9 | CPU Event mask on Event input x |
| PR10 | CPU Event mask on Event input x |
| PR11 | CPU Event mask on Event input x |
| PR12 | CPU Event mask on Event input x |
| PR13 | CPU Event mask on Event input x |
| PR14 | CPU Event mask on Event input x |
| PR15 | CPU Event mask on Event input x |
| PR16 | CPU Event mask on Event input x |
| PR17 | CPU Event mask on Event input x |
| PR18 | CPU Event mask on Event input x |
| PR19 | CPU Event mask on Event input x |
| PR20 | CPU Event mask on Event input x |
| PR21 | CPU Event mask on Event input x |