Instruction Manual

1 of 20 022101
FEATURES
 Integrated NV SRAM, real time clock,
crystal, power-fail control circuit and lithium
energy source
 Clock registers are accessed identically to the
static RAM; these registers are resident in the
16 top RAM locations
 Century byte register; i.e., Y2K complaint
 Totally nonvolatile with over 10 years of
operation in the absence of power
 Precision power-on reset
 Programmable watchdog timer and RTC
alarm
 BCD coded 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 ±10%
V
CC
power supply tolerance
 Lithium energy source is electrically
disconnected to retain freshness until power is
applied for the first time
PIN ASSIGNMENT
DS1554
256K NV Y2KC Timekeeping RAM
www.dalsemi.com
1
IRQ/FT
2
3
NC
NC
RST
V
CC
WE
OE
CE
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
GND
4
5
6
7
8
9
10
11
12
13
14
15
16
17
NC
A
14
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
A
13
A
12
A
11
A
10
A
9
A
8
A
7
A
6
A
5
A
4
A
3
A
2
A
1
A
0
34
NC
X1 GND
V
BAT
X2
34-Pin PowerCap
®
Module Board
(Uses DS9034PCX PowerCap)
RST
13
1
2
3
4
5
6
7
8
9
10
11
12
14
31
A14
A7
A5
A4
A3
A2
A1
A0
DQ1
DQ0
V
CC
NC
IRQ/FT
WE
A
13
A
8
A
9
A
11
OE
A
10
CE
DQ7
DQ5
DQ6
32
30
29
28
27
26
25
24
23
22
21
19
20
NC
A12
A6
DQ2
GND
15
16
18
17
DQ4
DQ3
32-Pin Encapsulated Package