DS1554 Datasheet, PDF (2/21 Pages) Dallas Semiconductor – 256K NV Y2KC Timekeeping RAM

ORDERING INFORMATION
DS1554P-XXX
(5-Volt)
-70 70 ns access
-100 100 ns access
DS1554
blank 32-pin DIP Module
P 34-pin PowerCap Module
board*
*DS1554WP-XXX (3.3 Volt)
-120 120 ns access
-150 150 ns access
blank 32-pin DIP Module
P 34-pin PowerCap Module
board*
*DS9034PCX (PowerCap) Required:
must be ordered seperately
PIN DESCRIPTION
A0-A14
- Address Input
DQ0-DQ7
- Data Input/Outputs
IRQ \FT
- Interrupt, Frequency Test Output
(Open Drain)
RST
- Power-On Reset Output
(Open Drain)
CE
- Chip Enable
OE
- Output Enable
WE
V_CC
GND
NC
X1, X2
V_BAT
- Write Enable
- Power Supply Input
- Ground
- No Connection
- Crystal Connection
- Battery Connection
DESCRIPTION
The DS1554 is a full function, year 2000-compliant (Y2KC), real-time clock/calendar (RTC) with a RTC
alarm, watchdog timer, power-on reset, battery monitor, and 32k x 8 non-volatile static RAM. User
access to all registers within the DS1554 is accomplished with a bytewide interface as shown in Figure 1.
The RTC Registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour
BCD format. Corrections for day of month and leap year are made automatically.
The RTC Registers are double-buffered into an internal and external set. The user has direct access to the
external set. Clock/calendar updates to the external set of registers can be disabled and enabled to allow
the user to access static data. Assuming the internal oscillator is turned on, the internal set of registers are
continuously updated; this occurs regardless of external registers settings to guarantee that accurate RTC
information is always maintained.
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