Here is a picture of signals between motherboard and rtc clock. RTC uses Intel timing protocol. Pulse duration is about 1µs and time between pulses are about 24µs. AS means Address Select. It functions like clock signal. When DS is low then motherboard wants to read rtc and when RW is low motherboard wants to write to rtc memory. Data protocol is same as generic RAM memory. All this is valid only if MOT pin is connected low. Otherwise Motorola timing is used and it is completely different.