DS1642-85 MAXIM [Maxim Integrated Products], DS1642-85 Datasheet - Page 2

• Manufacturer Part Number: DS1642-85
• Description: Nonvolatile Timekeeping RAM
• Manufacturer: MAXIM [Maxim Integrated Products]

PIN DESCRIPTION
DESCRIPTION
The DS1642 is a 2k x 8 nonvolatile static RAM and a full-function real-time clock (RTC), both of which
are accessible in a bytewide format. The nonvolatile time keeping RAM is pin and function equivalent to
any JEDEC-standard 2k x 8 SRAM. The device can also be easily substituted in ROM, EPROM, and
EEPROM sockets, providing read/write nonvolatility and the addition of the real-time clock function. The
real-time clock information resides in the eight uppermost RAM locations. The RTC registers contain
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. 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
DS1642 also contains its own power-fail circuitry, which deselects the device when the V
an out-of-tolerance condition. This feature prevents loss of data from unpredictable system operation
brought on by low V
PIN
19
22
23
10
11
13
14
15
16
17
12
18
20
21
24
1
2
3
4
5
6
7
8
9
NAME
GND
DQ0
DQ1
DQ2
DQ3
DQ4
DQ5
DQ6
DQ7
A10
V
WE
OE
A7
A6
A5
A4
A3
A2
A1
A0
A9
A8
CE
CC
CC
Address Input
Data Input/Output
Ground
Active-Low Chip-Enable Input
Active-Low Output-Enable Input
Active-Low Write-Enable Input
Power-Supply Input
as errant access and update cycles are avoided.
FUNCTION
2 of 13
CC
supply is in
DS1642