Datasheet

Clock operation M41ST87Y, M41ST87W
30/54 Doc ID 9497 Rev 10
3.1 TIMEKEEPER
®
registers
The M41ST87Y/W offers 22 internal registers which contain clock, control, alarm, watchdog,
flag, square wave, and tamper data. The 8 clock registers are memory locations which
contain external (user accessible) and internal copies of the data (usually referred to as
BiPORT
™
TIMEKEEPER cells). The external copies are independent of internal functions
except that they are updated periodically by the simultaneous transfer of the incremented
internal copy. The internal divider (or clock) chain will be reset upon the completion of a
WRITE to any clock address (00h to 07h).
The system-to-user transfer of clock data will be halted whenever the address being
accessed is a clock address (00h to 07h). The updates will resume either due to a stop
condition or when the pointer increments to a non-clock or RAM address.
TIMEKEEPER and alarm registers store data in BCD format. Control, watchdog and square
wave registers store data in binary format.
Table 7. TIMEKEEPER
®
register map
Addr
Data
Function/range
BCD format
D7 D6 D5 D4 D3 D2 D1 D0
00h 0.1 seconds 0.01 seconds
10s/100s
seconds
00-99
01h ST 10 seconds Seconds Seconds 00-59
02h OFIE 10 minutes Minutes Minutes 00-59
03h CB1 CB0 10 hours Hours (24-hour format)
Century/
Hours
0-1/
00-23
04h TR THS CLRPW1 CLRPW0 32kE Day of week Day 01-7
05h PFOD 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 Control
09h WDS BMB4 BMB3 BMB2 BMB1 BMB0 RB1 RB0 Watchdog
0Ah AFE SQWE ABE Al 10M 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 TB1 TB2 Flags
10h 0 0 0 0 0 0 0 0 Reserved
11h 0 0 0 0 0 0 0 0 Reserved
12h 0 0 0 0 0 0 0 0 Reserved
13h RS3 RS2 RS1 RS0 SQWOD 0 0 0 SQW
14h TEB1 TIE1 TCM1 TPM1 TDS1
TCHI/
TCLO
1
CLR1
EXT
CLR1 Tamper1
15h TEB2 TIE2 TCM2 TPM2 TDS2
TCHI/
TCLO
2
CLR2
EXT
CLR2 Tamper2
16h-1Dh ROM
Serial
number
8-byte
1Eh-1Fh Reserved 2-byte
20h-9Fh
128 user
bytes