The recognition pattern is: C5h, 3Ah, A3h, 5Ch, C5h, 3Ah, A3h, 5Ch.
The Dobbertin RTC 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.
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