Ziatech Corporation ZT 8809A, Руководство по эксплуатации

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Real-Time Clock (DS 1215)
TIMEKEEPER REGISTER INFORMATION
Timekeeper information is contained in eight registers of 8 bits each
that are sequentially accessed one bit at a time after the 64-bit pattern
recognition sequence is completed. When updating the timekeeper
registers, each must be handled in groups of eight bits. Writing and
reading individual bits within a register could produce erroneous
results. These read/write registers are defined in Figure 10-3.
Reading or writing these registers is always accomplished by stepping
through all eight registers, starting with bit 0 of register 0 and ending
with bit 7 of register 7. All data in these registers is in BCD format,
with the exception of the upper four bits of register 3. When in 12-
hour mode, bit 5 of register 3 becomes an AM/PM indicator.
10-6