M48T35 데이터 시트보기 (PDF) - STMicroelectronics
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M48T35 Datasheet PDF : 26 Pages
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M48T35, M48T35Y
OPERATION MODES
As Figure 6., page 5 shows, the static memory ar-
ray and the quartz controlled clock oscillator of the
M48T35/Y are integrated on one silicon chip. The
two circuits are interconnected at the upper eight
memory locations to provide user accessible
BYTEWIDE clock information in the bytes with ad-
dresses 7FF8h-7FFFh.
The clock locations contain the year, month, date,
day, hour, minute, and second in 24 hour BCD for-
mat. Corrections for 28, 29 (leap year - valid until
2100), 30, and 31 day months are made automat-
ically. Byte 7FF8h is the clock control register. This
byte controls user access to the clock information
and also stores the clock calibration setting.
The eight clock bytes are not the actual clock
counters themselves; they are memory locations
consisting of BiPORT™ READ/WRITE memory
cells. The M48T35/Y includes a clock control cir-
cuit which updates the clock bytes with current in-
formation once per second. The information can
be accessed by the user in the same manner as
any other location in the static memory array.
The M48T35/Y also has its own Power-fail Detect
circuit. The control circuitry constantly monitors
the single 5V supply for an out of tolerance condi-
tion. When VCC is out of tolerance, the circuit write
protects the SRAM, providing a high degree of
data security in the midst of unpredictable system
operation brought on by low VCC. As VCC falls be-
low the Battery Back-up Switchover Voltage
(VSO), the control circuitry connects the battery
which maintains data and clock operation until val-
id power returns.
Table 2. Operating Modes
Mode
VCC
E
G
Deselect
VIH
X
WRITE
READ
4.75 to 5.5V
or
4.5 to 5.5V
VIL
X
VIL
VIL
READ
VIL
VIH
Deselect
VSO to VPFD (min)(1)
X
X
Deselect
≤ VSO(1)
X
X
Note: X = VIH or VIL; VSO = Battery Back-up Switchover Voltage.
1. See Table 11., page 18 for details.
W
DQ0-DQ7
X
High Z
VIL
DIN
VIH
DOUT
VIH
High Z
X
High Z
Power
Standby
Active
Active
Active
CMOS Standby
X
High Z Battery Back-up Mode
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