If I understand you right, you want to count relative slow pulses, but must save current.

Then I suggest e.g. the AT89S8252, which can wake up from power down by an external interrupt.

E.g. use a 74HC86 EXOR to feed your pulse into the interrupt input. And whenever the level changes, the 8252 wake up, do something and toggle the other input of the 74HC86 and go into power down again.

Then, if you have count the pulses inside the micro, you can do every arithmetic in software, which you want (also in floating point format).


Peter