¡ Semiconductor
MSM6542-01/02/03
MSM6542-01/02/03
DESCRIPTION
The MSM6542 is a perpetual-calendar-based
real time clock with an alarm function which
can read and write data in units of seconds. It
can be connected to various buses and can
function as a peripheral IC of a microcom-
puter.
The clock ranges are seconds, minutes, hours,
days, months, years, and days of the week.
The alarm ranges are seconds, minutes, hours,
days, months, and days of the week.
An event trigger is generated when the time
matches the specified time and an alarm oc-
curs or when the clock counter generates a
carry. The interrupt and pulse outputs are
provided for each of an alarm and a carry.
An interface with a microcomputer is imple-
mented by four data bus pins, four address
bus
¡ Semiconductor
REAL TIME CLOCK WITH PERIODIC AND ALARM OUTPUT
bus pins, three control bus pins, and two chip
select pins. These pins are used to write or
read data from the clock, alarm, and control
registers, or to modify the data.
The MSM6542 has an address latch enable
(ALE) input pin, allowing the data bus and
address bus to be shared. When the ALE
input pin is kept high, the data bus and ad-
dress bus can be exclusively used.
Other functions of the MSM6542 are: a 30-
second adjustment, stop and restart of clock,
data registers as RAM, and data register (RAM)
protection.
The CMOS circuitry used in the MSM6542
affords low power dissipation. The crystal
oscillator operates at 32.768 kHz. Provisions
for backup time keeping are included.
FEATURES
• Real time clock providing seconds, minutes,
hours, days, months, years, and days of
the week.
• Multiple alarm ranges covering seconds,
minutes, hours, days, months, and days of
the week. A desired alarm range can be
selected.
• A periodic interrupt output interval can
be selected over a wide range from 1/1024
seconds up to 10 minutes.
• Interface flexibility allows for connection
to many types of microprocessors.
• Single read-out procedure (Read flag).
• Single power sense circuitry. (Data protect
function).
• Unused registers can be used as RAM.
• 30-second adjustment by software or
hardware (software only for the MSM6542-
1/-2).
• Stop and restart of clock by software or
hardware (software only for the MSM6542-
1/-2).
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• 1 Hz output for adjustment and check of
oscillation frequency (MSM6542-3 only).
• User selection of 12 or 24 hour clock mode.
• Address latch enable (ALE) input pin.
• Advanced CMOS circuitry allows low
stand-by voltage and current.
• User standard 32.768 kHz oscillator crys-
tal
• Available in multiple packages
18-pin plastic DIP (for the MSM6542-
1RS/2RS) (DIP18-P-300).
20-pin plastic SOP (for the MSM6542-
1MS-K/2MS-K) (SSOP20-P-250-K).
24-pin plastic DIP (for the MSM6542-
3RS) (DIP24-P-600).
24-pin plastic SOP (for the MSM6542-
3GS-VK) (SOP24-P-430-VK).
• Pin assignment compatibility with the
MSM6242BRS (The MSM6542-3MSK pro-
vides near compatibility.).
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