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Real-Time Clock: Clock Operation
KAT4000 User’s Manual 10007175-02
11-2
7 Years register
8 Control register
The M41T00 clock continually monitors the supply voltage (Vcc) for an out of tolerance
condition. If Vcc falls below switch-over voltage (Vso), the M41T00:
• Terminates an access in progress
• Resets the device address counter
• Does not recognize inputs (prevents erroneous data from being written)
At power-up, the M41T00 uses Vcc at Vso and recognizes inputs.
CLOCK OPERATION
Read the seven Clock registers one byte at a time or in a sequential block. Access the Con-
trol register (address location 7) independently. An update to the Clock registers is delayed
for 250 ms to allow the read to be completed before the update occurs. This delay does not
alter the actual clock time. The eight byte clock register sets the clock and reads the date
and time from the clock, as summarized in
Tab le 1 1 -1 .
Table 11-1: RTC Register Map
ST: Stop bit
1Stops the oscillator
0 Restarts the oscillator within one second
CEB: Century Enable Bit
1 Causes CB to toggle either from 0 to 1 or from 1 to 0 at the turn of the century
0 CB will not toggle
CB: Century Bit
Address: Data: Function/Range:
D7 D6 D5 D4 D3 D2 D1 D0 BCD Format
00
ST 10 Seconds Seconds Seconds 00—59
01
X 10 Minutes Minutes Minutes 00—59
02
CEB CB 10 Hours Hours Century/
Hours
0-1/
00-23
03
XXXXX Day Day01—07
04
X X 10 Date Date Date 01—31
05
X X X 10 M Month Month 01—12
06
10 Years Years Years 00—99
07
OUT FT S Calibration Control —