BQ3285_15 Datasheet, PDF (4/26 Pages) Texas Instruments – Real-Time Clock (RTC)

bq3285
Functional Description
Address Map
The bq3285 provides 14 bytes of clock and control/status
registers and 114 bytes of general nonvolatile storage.
Figure 1 illustrates the address map for the bq3285.
Update Period
The update period for the bq3285 is one second. The
bq3285 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 bq3285 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.
14
Bytes
0
00
Clock and
Control Status
Registers
13
0D
14
0E
114
Bytes
Storage
Registers
127
7F
0
Seconds
00
1 Seconds Alarm 01
2
Minutes
02
3 Minutes Alarm 03
4
Hours
04
5 Hours Alarm 05
6 Day of Week 06
7 Day of Month 07
8
Month
08
9
Year
09
10
Register A
0A
11
Register B
0B
12
Register C
0C
13
Register D
0D
BCD or
Binary
Format
Figure 1. Address Map
Update Period
(1s)
UIP
t_BUC
tUC (Update Cycle)
Figure 2. Update Period Timing and UIP
4