19.1.2 16-Bit Mode

In this mode, Timer0 increments on the rising edge of the selected clock source. A prescaler on the clock input gives several prescale options (see the prescaler control bits, CKPS). In this mode, TMR0H:TMR0L form the 16-bit timer value. As shown in Figure 19-1, reads and writes of the TMR0H register are buffered. The TMR0H register is updated with the contents of the high byte of Timer0 when the TMR0L register is read. Similarly, writing the TMR0L register causes a transfer of the TMR0H register value to the Timer0 high byte.

This buffering allows all 16 bits of Timer0 to be read and written at the same time. Timer0 rolls over to 0x0000 on incrementing past 0xFFFF. This makes the timer free-running. While actively operating in 16-bit mode, the Timer0 value can be read but not written.