DS1215 データシートの表示（PDF） - Dallas Semiconductor -> Maxim Integrated
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DS1215 Datasheet PDF : 15 Pages
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DS1215
When the first write cycle is executed, it is compared to
bit 1 of the 64–bit comparison register. If a match is
found, the pointer increments to the next location of the
comparison register and awaits the next write cycle. If a
match is not found, the pointer does not advance and all
subsequent write cycles are ignored. If a read cycle oc-
curs at any time during pattern recognition, the present
sequence is aborted and the comparison register point-
er is reset. Pattern recognition continues for a total of 64
write cycles as described above until all the bits in the
comparison register have been matched. (This bit pat-
tern is shown in Figure 2.) With a correct match for 64
bits, the Time Chip is enabled and data transfer to or
from the timekeeping registers may proceed. The next
64 cycles will cause the Time Chip to either receive data
on D, or transmit data on Q, depending on the level of
OE pin or the WE pin. Cycles to other locations outside
the memory block can be interleaved with CEI cycles
without interrupting the pattern recognition sequence or
data transfer sequence to the Time Chip.
A 32,768 Hz quartz crystal can be directly connected to
the DS1215 via pins 1 and 2 (X1, X2). The crystal se-
lected for use should have a specified load capacitance
(CL) of 6 pF. For more information on crystal selection
and crystal layout considerations, please consult
Application Note 58, “Crystal Considerations with Dal-
las Real Time Clocks”.
TIME CHIP COMPARISON REGISTER DEFINITION Figure 2
HEX
VALUE
7
6
5
4
3
2
1
0
BYTE 0
1
1
0
0
0
1
0
1
C5
BYTE 1
0
0
1
1
1
0
1
0
3A
BYTE 2
1
0
1
0
0
0
1
1
A3
BYTE 3
BYTE 4
0
1
0
1
1
1
0
0
5C
1
1
0
0
0
1
0
1
C5
BYTE 5
BYTE 6
0
0
1
1
1
0
1
0
3A
1
0
1
0
0
0
1
1
A3
BYTE 7
0
1
0
1
1
1
0
0
5C
NOTE:
The pattern recognition in Hex is C5, 3A, A3, 5C, C5, 3A, A3, 5C. The odds of this pattern being accidentally duplicated
and causing inadvertent entry to the Time Chip are less than 1 in 1019.
032697 3/15
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