DS1307 not running?

[richard]

the ds1307 has 8 registers for the rtc function addressed from 0 to 0x07
the control reg address is 0x07 bits 7 and 4 control the sqwe , if you only use the time keeping function the control reg can be ignored
to set the time you start at register address 0 (sec min hours ......)
to read just minutes start from address 1 etc
pbp will set bit 0 of the device address ($d0 in this case) as required (at least pbp3 will not sure about pbp2xx)

the ram goes from 0x08 to 0x3f trying to write or read from regs $d0 or $d1 will not have meaning full results