In the Device Data Sheet (DS39632 C), the following clarifications and corrections should be noted. Any silicon issues for the PIC18F2455/2550/4455/4550 will be reported in a separate silicon errata. Please check the Microchip web site for any existing issues. PIC18F2455/2550/4455/4550 PIC18F2455/2550/4455/4550 Data Sheet Errata Clarifications/Corrections to the Data 1. Module: Timer1 Module Sheet: The Real-Time Clock application example, cited in In the Device Data Sheet (DS39632C), the following Section 12.6 “Using Timer1 as a Real-Time clarifications and corrections should be noted. Any Clock,” has changed. silicon issues for the PIC18F2455/2550/4455/4550 will “Example 12-1: Implementing a Real-Time be reported in a separate silicon errata. Please check Clock Using a Timer1 Interrupt Service” is the Microchip web site for any existing issues. ……