BQ3285EC Datasheet, PDF (4/26 Pages) Texas Instruments – Real-Time Clock (RTC)

bq3285EC/LC
Functional Description
Address Map
The bq3285EC/LC provides 14 bytes of clock and con-
trol/status registers and 242 bytes of general nonvolatile
storage. Figure 1 illustrates the address map for the
bq3285EC/LC.
Update Period
The update period for the bq3285EC/LC is one second.
The bq3285EC/LC updates the contents of the clock and
calendar locations during the update cycle at the end of
each update period (see Figure 2). The alarm flag bit
may also be set during the update cycle.
The bq3285EC/LC copies the local register updates into
the user buffer accessed by the host processor. When a 1
is written to the update transfer inhibit bit (UTI) in reg-
ister B, the user copy of the clock and calendar bytes re-
mains unchanged, while the local copy of the same bytes
continues to be updated every second.
The update-in-progress bit (UIP) in register A is set
tBUC time before the beginning of an update cycle (see
Figure 2). This bit is cleared and the update-complete
flag (UF) is set at the end of the update cycle.
Figure 1. Address Map
Figure 2. Update Period Timing and UIP
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July 1996