M41T56(2006) 데이터 시트보기 (PDF) - STMicroelectronics
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M41T56 Datasheet PDF : 28 Pages
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Clock operation
3
Clock operation
M41T56
Note:
The eight byte clock register (see Table 3) is used to both set the clock and to read the date
and time from the clock, in a binary coded decimal format. Seconds, Minutes, and Hours are
contained within the first three registers. Bits D6 and D7 of Clock Register 2 (Hours
Register) contain the CENTURY ENABLE Bit (CEB) and the CENTURY Bit (CB). Setting
CEB to a '1' will cause CB to toggle, either from '0' to '1' or from '1' to '0' at the turn of the
century (depending upon its initial state). If CEB is set to a '0,' CB will not toggle. Bits D0
through D2 of Register 3 contain the Day (day of week). Registers 4, 5, and 6 contain the
Date (day of month), Month, and Years. The final register is the Control Register (this is
described in the Clock Calibration section). Bit D7 of Register 0 contains the STOP Bit (ST).
Setting this bit to a '1' will cause the oscillator to stop.
If the device is expected to spend a significant amount of time on the shelf, the oscillator
may be stopped to reduce current drain. When reset to a '0' the oscillator restarts within one
second.
The seven Clock Registers may be read one byte at a time, or in a sequential block. The
Control Register (Address location 7) may be accessed independently. Provision has been
made to assure that a clock update does not occur while any of the seven clock addresses
are being read. If a clock address is being read, an update of the clock registers will be
delayed by 250ms to allow the READ to be completed before the update occurs. This will
prevent a transition of data during the READ.
This 250ms delay affects only the clock register update and does not alter the actual clock
time.
Table 3. Register map(1)
Address
D7
Data
D6 D5 D4 D3 D2 D1 D0
Function/range
BCD format
0
ST
10 Seconds
Seconds
1
X
10 Minutes
2
CEB(2) CB
10 hours
Minutes
Hours
3
X
X
X
X
X
Day
4
X
X
10 date
Date
5
X
X
X 10 M.
Month
6
10 years
Years
7
OUT
FT
S
Calibration
Seconds
00-59
Minutes
00-59
Century/hours 0-1/00-23
Day
01-07
Date
01-31
Month
01-12
Year
00-99
Control
1. Keys:
S = SIGN Bit
FT = FREQUENCY TEST Bit
ST = STOP Bit
OUT = Output level
X = Don't care
CEB = Century Enable Bit
CB = Century Bit
2. When CEB is set to '1,' CB toggles from '0' to '1' or from '1' to '0' every 100 years (dependent upon the
initial value set). When CEB is set to '0,' CB does not toggle.
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