BQ4285_14 Datasheet, PDF (4/29 Pages) Texas Instruments – Real-Time Clock (RTC) With NVRAM Control

bq4285
Functional Description
Address Map
The bq4285 provides 14 bytes of clock and control/status
registers and 114 bytes of general nonvolatile storage.
Figure 1 illustrates the address map for the bq4285.
Update Period
The update period for the bq4285 is one second. The
bq4285 updates the contents of the clock and calendar
locations during the update cycle at the end of each up-
date period (see Figure 2). The alarm flag bit may also
be set during the update cycle.
The bq4285 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 regis-
ter 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
4