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Clock-calendar chip adds `wakeup'
Extra output pin can control a power switch while Vcc is off
A variant of an industry-standard clock-calendar RAM used in AT
motherboards, the DS1587 module comes with a unique 64-bit serial
identification number and a facility for initiating power up. The
power-up, or wakeup, can be initiated at a preset time and date, or every
day. It can also be initiated by an external signal. The wakeup feature
requires an external battery, separate from the battery that keeps the
clock and CMOS RAM setup when the machine is powered down. The wakeup
control pin actuates a solid-state power relay to turn on the computer.
When the wakeup alarm is active, a register storing the wakeup time/date
is compared with the clock counter. On a match, the power-on signal
becomes active. External activation could come from a modem ring signal.
The 64-bit serial identification number is burned into the calendar chip
with a laser. Users can reserve blocks of numbers to keep their equipment
in a series. The serial number could be used by network software to
identify stations. Total memory on the chip is 8 Kbytes plus 144 bytes.
The chip has all the other features of a standard clock-calendar. It comes
in a 28-pin DIP module with crystal and lithium battery in the package. It
also comes as a monolithic IC without crystal or battery, DS1585/S, in
28-pin DIP or SOIC. (DS1587, $15.50 ea/10,000; DS1585, $12 ea/10,
000–available now.) Dallas Semiconductor Dallas TX Jim Lott
214-450-0448
CAPTION:
The DS1587 clock-calendar module can actuate a power switch at a preset
time to automate unattended transactions.
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