DS1254 Maxim, DS1254 Datasheet - Page 2

• Manufacturer Part Number: DS1254
• Description: The DS1254 is a fully nonvolatile static RAM (NV SRAM) (organized as 2M words by 8 bits) with built-in real-time clock
• Manufacturer: Maxim

DETAILED DESCRIPTION
The DS1254 is a fully nonvolatile static RAM (NV SRAM) (organized as 2M words by 8 bits) with built-in real-time
clock. It has a self-contained lithium energy source and control circuitry that constantly monitors V
tolerance condition. When such a condition occurs, the DS1254 makes use of an attached DS3800 battery cap to
maintain clock information and preserve stored data while protecting that data by disallowing all memory accesses.
Additionally, the DS1254 has dedicated circuitry for monitoring the status of an attached DS3800 battery cap.
The phantom clock provides timekeeping information including hundredths of seconds, seconds, minutes, hours,
day, date, month, and year information. The date at the end of the month is automatically adjusted for months with
fewer than 31 days, including correction for leap years. The phantom clock operates in either 24-hour or 12-hour
format with an AM/PM indicator.
Because the DS1254 has a total of 168 balls and only 35 active signals, balls are wired together into groups, thus
providing redundant connections for every signal.
Figure 1. Pin Configuration
GND
V
A7
A6
A5
A4
A3
A2
A1
CC
V
BAT
1
2
3
4
5
6
7
8
9
Dallas Semiconductor
DS1254
2 of 17
RECEPTACLES FOR
DS3800 BATTERY CAP
PINS
GND
29
28
27
26
25
24
23
22
21
V
A17
A18
A19
GND
A20
CE
OE
WE
CC
CC
for an out-of-
DS1254