The Dobbertin chip requires 64 sequential writes with magic serial data on A0 to unlock it, immediately followed by 64 sequential reads to retrieve the 64-bit time data packet from D0, after which the chip locks itself back into ROM mode.
=== Register 0..7 Real-Time Clock Registers ===
{| class="wikitable" style="text-align:center;"
|+ Real-Time Clock Registers
|-
! rowspan="2" | Register !! colspan="8" | Bit Position !! rowspan="2" | Range (BCD)