DS1742
Y2KC Nonvolatile Timekeeping RAM
www.dalsemi.com
FEATURES
Integrated NV SRAM, real time clock,
crystal, power-fail control circuit and lithium
energy source
Clock registers are accessed identical to the
static RAM. These registers are resident in
the eight top RAM locations
Century byte register
Totally nonvolatile with over 10 years of
operation in the absence of power
BCD coded century, year, month, date, day,
hours, minutes, and seconds with automatic
leap year compensation valid up to the year
2100
Battery voltage level indicator flag
Power-fail write protection allows for
卤10%
V
CC
power supply tolerance
Lithium energy source is electrically
disconnected to retain freshness until power is
applied for the first time
Standard JEDEC bytewide 2k x 8 static RAM
pinout
Quartz accuracy
卤1
minute a month @ 25掳C,
factory calibrated
PIN ASSIGNMENT
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
V
CC
A8
A9
WE
OE
A10
CE
DQ7
DQ6
DQ5
DQ4
DQ3
PIN DESCRIPTION
A0-A10
CE
OE
WE
V
CC
GND
DQ0-DQ7
- Address Inputs
- Chip Enable
- Output Enable
- Write Enable
- Power Supply Input
- Ground
- Data Input/Outputs
ORDERING INFORMATION
DS1742-XXX
(5V)
-70
-100
70 ns access
100 ns access
DS1742W-XXX
(3.3V)
-120 120 ns access
-150 150 ns access
DESCRIPTION
The DS1742 is a full function, year 2000-compliant (Y2KC), real-time clock/calendar (RTC) and 2k x 8
non-volatile static RAM. User access to all registers within the DS1742 is accomplished with a bytewide
interface as shown in Figure 1. The Real Time Clock (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 day of the month and leap year
are made automatically.
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