DS1557 Maxim, DS1557 Datasheet - Page 3

• Manufacturer Part Number: DS1557
• Description: The DS1557 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) with an RTC alarm, watchdog timer, power-on reset, battery monitor, and 512k x 8 nonvolatile static RAM
• Manufacturer: Maxim

Figure 1. Block Diagram
Table 1. Operating Modes
DATA READ MODE
The DS1557 is in the read mode whenever CE (chip enable) is low and WE (write enable) is high. The
device architecture allows ripple-through access to any valid address location. Valid data will be available
at the DQ pins within t
satisfied. If CE or OE access times are not met, valid data will be available at the latter of chip enable
access (t
controlled by CE and
intermediate state until t
will remain valid for output data hold time (t
access.
V
V
SO
CC
V
< V
< V
CC
V
CEA
> V
CC
CC
SO
) or at output enable access time (t
<V
<V
PF
PF
PF
V
V
V
V
CE
X
X
AA
IH
IL
IL
IL
AA
OE
after the last address input is stable, providing that CE and OE access times are
. If the address inputs are changed while CE and OE remain valid, output data
. If the outputs are activated before t
V
V
OE
X
X
X
X
IH
IL
WE
V
V
V
X
X
X
IH
IH
IL
DQ0–DQ7
HIGH-Z
HIGH-Z
HIGH-Z
HIGH-Z
D
D
OUT
OH
IN
) but will then go indeterminate until the next address
3 of 17
OEA
). The state of the data input/output pins (DQ) is
Data Retention
Deselect
Deselect
MODE
Write
Read
Read
AA
, the data lines are driven to an
CMOS Standby
Battery Current
POWER
Standby
Active
Active
Active
DS1557
Maxim