DS1554 Datasheet, PDF (3/21 Pages) Dallas Semiconductor – 256K NV Y2KC Timekeeping RAM

DS1554
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.
The DS1554 also contains its own power-fail circuitry which automatically deselects the device when the
V_CC supply enters an out of tolerance condition. This feature provides a high degree of data security
during unpredictable system operation brought on by low V_CC levels.
PACKAGES
The DS1554 is available in two packages (32-pin DIP and 34-pin PowerCap module). The 32-pin DIP
style module integrates the crystal, lithium energy source, and silicon all in one package. The 34-pin
PowerCap module board is designed with contacts for connection to a separate PowerCap (DS9034PCX)
that contains the crystal and battery. This design allows the PowerCap to be mounted on top of the
DS1554P after the completion of the surface mount process. Mounting the PowerCap after the surface
mount process prevents damage to the crystal and battery due to the high temperatures required for solder
reflow. The PowerCap is keyed to prevent reverse insertion. The PowerCap Module board and PowerCap
are ordered separately and shipped in separate containers. The part number for the PowerCap is
DS9034PCX.
DS1554 BLOCK DIAGRAM Figure 1
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