25.9 Timer1 Operation During Sleep

Timer1 can only operate during Sleep when configured as an asynchronous counter. In this mode, many clock sources can be used to increment the counter. To set up the timer to wake the device:

  • The ON bit must be set
  • The TMRxIE bit of the PIEx register must be set
  • Global interrupts must be enabled
  • The SYNC bit must be set
  • Configure the TxCLK register for using any clock source other than FOSC and FOSC/4

The device will wake up on an overflow and execute the next instruction. If global interrupts are enabled, the device will call the IRS. The secondary oscillator will continue to operate in Sleep regardless of the SYNC bit setting.