The TMR0IF interrupt flag bit of the INTCON register is set every time the TMR0 register overflows from FFh to 00h, regardless of whether or not the Timer0 interrupt is enabled. This allows the software to poll the bit asynchronously. The TMR0IF bit is not automatically reset, it needs to be cleared in the software.
When TMR0IF is set?
PIC18 has the ability to generate interrupt on overflow. It means that a bit called Timer0 Interrupt Flag (TMR0IF) is set when TMR0 makes transition from 255 to 0.
What TMR0ON means?
TMR0ON = 1; When the counter counts up from 216-1 to 0, is is said to roll-over. ... This flag is sticky, meaning that once it's set by the 16-bit counter rolling over, it stays set until the user clears it in software. The TMR0IF bit is cleared by writing a 0 to that value.
