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Real-Time Clock: Clock Operation
Katana
®
752i User’s Manual 10006024-04
7-2
1 Seconds register
2 Minutes register
3 Century/Hours register
4 Day register
5 Date register
6 Month register
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
Table 7-1.
Table 7-1: RTC Register Map
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 X XXXXDay Day 01—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 —