What I think you need to do is "eavesdrop" on the clock and data line.

Eg wait for the clock to change from idle state, read the data line and store the bit, wait for clock change back to idle state,wait for the clock to change from idle state, read the data bit and store it.......................keep going until you have the data you need.

See the manual http://melabs.com/resources/pbpmanual/5_65-5_70.htm and the clock and date illustration