BQ4285E_14 datasheet(4/31 Pages) TI1

Part #	BQ4285E

Description	Enhanced RTC With NVRAM Control

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Manufacturer	TI1 [Texas Instruments]

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Functional Description

Address Map

The bq4285E/L provides 14 bytes of clock and con-

trol/status registers and 114 bytes of general nonvolatile

storage.

Figure 1 illustrates the address map for the

bq4285L.

Update Period

The update period for the bq4285E/L is one second. The

bq4285E/L updates the contents of the clock and calen-

dar 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 bq4285E/L copies the local register updates into the

user buffer accessed by the host processor. Whena1is

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.

4

Figure 1. Address Map

Figure 2. Update Period Timing and UIP

bq4285E/L

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