DS1747 Datasheet, PDF (2/18 Pages) Dallas Semiconductor – Y2K-Compliant, Nonvolatile Timekeeping RAMs

DS1747/DS1747P Y2K-Compliant, Nonvolatile Timekeeping RAMs
PIN DESCRIPTION
A0–A18
CE
OE
WE
– Address Input
– Chip Enable
– Output Enable
– Write Enable
V_CC
GND
– Power-Supply Input
– Ground
DQ0–DQ7 – Data Input/Output
N.C.
– No Connection
RST
– Power-On Reset Output (PowerCap Module board only)
X1, X2
– Crystal Connection
V_BAT
– Battery Connection
ORDERING INFORMATION
PART
TEMP RANGE PIN-PACKAGE
DS1747-70
0°C to +70°C 32 EDIP (0.740a)
DS1747-70IND
-40°C to +85°C 32 EDIP (0.740a)
DS1747P-70
0°C to +70°C 34 PowerCap
DS1747P-70IND
-40°C to +85°C 34 PowerCap
DS1747W-120
0°C to +70°C 32 EDIP (0.740a)
DS1747W-120IND
-40°C to +85°C 32 EDIP (0.740a)
DS1747WP-120
0°C to +70°C 34 PowerCap
DS1747WP-120IND -40°C to +85°C 34 PowerCap
TOP MARK
DS1747-70
DS1747-70 IND
DS1747P-70
DS1747P-70 IND
DS1747W-120
DS1747W-120 IND
DS1747WP-120
DS1747WP-120 IND
DESCRIPTION
The DS1747 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) and
512k x 8 nonvolatile static RAM. User access to all registers within the DS1747 is accomplished with a
byte-wide interface as shown in Figure 1. The RTC information and control bits reside in the eight
uppermost RAM locations. The RTC registers contain century, year, month, date, day, hours, minutes,
and seconds data in 24-hour BCD format. Corrections for the date of each month and leap year are made
automatically. The RTC clock registers are double buffered to avoid access of incorrect data that can
occur during clock update cycles. The double-buffered system also prevents time loss as the
timekeeping countdown continues unabated by access to time register data. The DS1747 also contains
its own power-fail circuitry that deselects the device when the V_CC supply is in an out-of-tolerance
condition. This feature prevents loss of data from unpredictable system operation brought on by low V_CC
as errant access and update cycles are avoided.
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