DS1644 Maxim, DS1644 Datasheet - Page 6

• Manufacturer Part Number: DS1644
• Description: The DS1644 is a 32k x 8 nonvolatile static RAM with a full function real time clock, which are both accessible in a byte-wide format
• Manufacturer: Maxim

DS1644/DS1644P
DATA RETENTION MODE
When V
is within nominal limits (V
> 4.5 volts) the DS1644 can be accessed as described above with
CC
CC
read or write cycles. However, when V
is below the power-fail point V
(point at which write
CC
PF
protection occurs) the internal clock registers and RAM are blocked from access. This is accomplished
internally by inhibiting access via the
signal. At this time the power-fail output signal (
) will be
CE
PFO
driven active low and will remain active until V
returns to nominal levels. When V
falls below the
CC
CC
level of the internal battery supply, power input is switched from the V
pin to the internal battery and
CC
clock activity, RAM, and clock data are maintained from the battery until V
is returned to nominal
CC
level.
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