Hi,
OK, so the 12F615 has the TMR1 Gate feature, I'd say you're good to go for an all hardware solution - and since there's no pulses on second line when the first line isn't high then it gets even easier.

Set up TMR1 as a timer with the gate control enabled, clear it and feed the "long" pulse to the gate control pin, this will measure the duration of the long pulse. Set TMR0 up as a counter, clear it and feed the pulses to the counter input, this will count the number of pulses.

If you use the comparator as the gate control for TMR1 you might be able to set an interrupt up to trip when the duration of the long pulse ends.

/Henrik.