Timing Diagram. number 5 is dailed
* * * *| Dial is stationary | Dial is rotated to number |* Dail is released* | Dial stops
* * * * * * * * * * * * * * *________________________________________________
latch ______________________/* * * * * * * * * * * * * * * * * * * * * * * * \____________
* * * __________________________________________________* *_* *_* *_* *_* *_______________
pulse* * * * * * * * * * * * * * * * * * * * * * * * * *\_/ \_/ \_/ \_/ \_/
3 simple rules:
- If pulse changes from low to high, increment a counter
- If latch changes from low to high, reset the counter
- If latch changes from high to low, the number is added
* to a circular buffer and the buffer is compared to the pin code