M41T81 Datasheet, PDF (16/28 Pages) STMicroelectronics – Serial Access Real-Time Clock with Alarms

M41T81
Table 10. TIMEKEEPER^® Register Map
Addr
D7
D6
D5
D4
00h
0.1 Seconds
01h
ST
10 Seconds
02h
0
10 Minutes
03h CEB
CB
10 Hours
04h
0
0
0
0
05h
0
0
10 Date
06h
0
0
0
10M
07h
10 Years
08h OUT
FT
S
09h
0
BMB4 BMB3 BMB2
0Ah AFE SQWE ABE Al 10M
0Bh RPT4 RPT5
AI 10 Date
0Ch RPT3
HT
AI 10 Hour
0Dh RPT2
Alarm 10 Minutes
0Eh RPT1
Alarm 10 Seconds
0Fh WDF
AF
0
0
10h
0
0
0
0
11h
0
0
0
0
12h
0
0
0
0
13h RS3
RS2
RS1
RS0
Keys: S = Sign Bit
FT = Frequency Test Bit
ST = Stop Bit
0 = Must be set to '0'
BMB0-BMB4 = Watchdog Multiplier Bits
CEB = Century Enable Bit
CB = Century Bit
OUT = Output level
ABE = Alarm in Battery Back-up Mode Enable Bit
Function/Range
D3
D2
D1
D0
BCD Format
0.01 Seconds
Seconds 00-99
Seconds
Seconds 00-59
Minutes
Minutes 00-59
Hours (24 Hour Format)
Century/
Hours
0-1/00-23
0
Day of Week
Day
01-7
Date: Day of Month
Date
01-31
Month
Month
01-12
Year
Year
00-99
Calibration
Control
BMB1 BMB0 RB1
RB0 Watchdog
Alarm Month
Al Month 01-12
Alarm Date
Al Date 01-31
Alarm Hour
Al Hour 00-23
Alarm Minutes
Al Min
00-59
Alarm Seconds
Al Sec
00-59
0
0
0
0
Flags
0
0
0
0
Reserved
0
0
0
0
Reserved
0
0
0
0
Reserved
0
0
0
0
SQW
AFE = Alarm Flag Enable Flag
RB0-RB1 = Watchdog Resolution Bits
RPT1-RPT5 = Alarm Repeat Mode Bits
WDF = Watchdog Flag (Read only)
AF = Alarm Flag (Read only)
SQWE = Square Wave Enable
RS0-RS3 = SQW Frequency
HT = Halt Update Bit
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