Control register 1
| I2CEN | Peripheral enable |
| PERMODE | I2C peripheral mode |
| SMBMODE | SMBus device mode |
| ARPEN | SMBus address resolution protocol enable |
| PECEN | PEC calculation enable |
| GCAEN | General call address enable |
| STRETCH | Clock stretching mode |
| GENSTART | Start generation |
| GENSTOP | Stop generation |
| ACKEN | Acknowledge enable |
| MACKCTRL | Master receiving mode acknowledge control |
| PECTEN | Request PEC transmission enable |
| SMBALERT | SMBus alert pin set |
| RESET | I2C peripheral reset |