Datasheet

M41T81S Clock operation
Doc ID 10773 Rev 7 15/32
Table 2. Clock register map
0 = Must be set to '0'
ABE = Alarm in battery backup mode enable bit
AF = Alarm flag (read only)
AFE = Alarm flag enable flag
BL = Battery low bit
BMB0-BMB4 = Watchdog multiplier bits
CB = Century bit
CEB = Century enable bit
FT = Frequency test bit
HT = Halt update bit
OF = Oscillator fail flag
OFIE = Oscillator fail interrupt enable
OUT = Output level
RB0-RB1 = Watchdog resolution bits
RPT1-RPT5 = Alarm repeat mode bits
RS0-RS3 = SQW frequency
S = Sign bit
SQWE = Square wave enable
ST = Stop bit
WDF = Watchdog flag (read only)
Addr
Function/range BCD
format
D7 D6 D5 D4 D3 D2 D1 D0
00h 0.1 seconds 0.01 Seconds Seconds 00-99
01h ST 10 seconds Seconds Seconds 00-59
02h 0 10 minutes Minutes Minutes 00-59
03h CEB CB 10 hours Hours (24-hour format) Century/hours 0-1/00-23
04h00000 Day of week Day 01-7
05h 0 0 10 date Date: day of month Date 01-31
06h 0 0 0 10M Month Month 01-12
07h 10 years Year Year 00-99
08h OUT FT S Calibration Calibration
09h OFIE BMB4 BMB3 BMB2 BMB1 BMB0 RB1 RB0 Watchdog
0Ah AFE SQW ABE Al Alarm month Al month 01-12
0Bh RPT4 RPT5 AI 10 date Alarm date Al date 01-31
0Ch RPT3 HT AI 10 hour Alarm hour Al hour 00-23
0Dh RPT2 Alarm 10 minutes Alarm minutes Al min 00-59
0Eh RPT1 Alarm 10 seconds Alarm seconds Al sec 00-59
0Fh WDF AF 0 BL 0 OF 0 0 Flags
10h00000000Reserved
11h00000000Reserved
12h00000000Reserved
13h RS3 RS2 RS1 RS0 0 0 0 0 SQW