TImer Interrupt
hello john2020,
Are you using a PIC MPU?
If you are the following must be done: I assumed that both External RBO interrupt and Timer Overflow Interrupt are both Enabled.
a.) during an interrupt you check first the INTCON, TOIF if it is SET to see if the interrupt is timer overflow, otherwise the interrupt must have been caused by external trigger on RB0 pin.
b.) The last thing you do before exiting you Interrupt service routine and enabling again all interrupts to occur, be sure to CLEAR the TOIF( Timer overflow interrupt flag) so that the next overflow will be detected, otherwise if TOIF is still SET, it won't cause an interrupt. Be sure also to CLEAR also the RB0 Interrupt flag after processing the interrupt.
All interrupt flag bits can be found at the INTCON register.
hope this help