Rainbow Electronics DS1554 - Manual (Page 2)

DS1554
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ORDERING INFORMATION
DS1554 5V; 32-pin DIP Module
DS1554P 5V; 34-pin PowerCap Module board*
DS1554W 3.3V; 32-pin DIP Module
DS1554WP 3.3V; 34-pin PowerCap Module board*
*DS9034PCX (PowerCap) Required:
must be ordered separately
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 - Write Enable
V
CC
- Power Supply Input
GND - Ground
NC - No Connection
X1, X2 - Crystal Connection
V
BAT
- 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.
The DS1554 has interrupt ( IRQ /FT) and reset ( RST ) outputs which can be used to control CPU activity.
The IRQ /FT interrupt output can be used to generate an external interrupt when the RTC Register values
match user programmed alarm values. The interrupt is always available while the device is powered from
the system supply and can be programmed to occur when in the battery backed state to serve as a system
wake-up. Either the
IRQ /FT or RST outputs can also be used as a CPU watchdog timer, CPU activity is
monitored and an interrupt or reset output will be activated if the correct activity is not detected within
programmed limits. The DS1554 power-on reset can be used to detect a system power down or failure
and hold the CPU in a safe reset state until normal power returns and stabilizes; the
RST output is used
for this function.