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GE - CMOS Real-Time Clock

Numéro de référence CDP1879
Description CMOS Real-Time Clock
Fabricant GE 
Logo GE 





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CDP1879 fiche technique
CMOS Peripherals
CDP1879, CDP1879C-1
iN'f
RESET
POWER DOWN
iii)
X-O/MEM
TPB/Wii
TPA
CS
A2
AI
AD
VSS'
I
2
5
4
5
6
7
B
9
10
II
12
24 VDD
23 XTAL
22 XTAL
21
CLOCK
OUT
20 DB7
19 DBS
IB DBS
17 OB4
16 OB3
15 OB2
14 OBl
15 OBO
92CS-54345RI
TERMINAL ASSIGNMENT
CMOS Real-Time Clock
Features
• CPU interface for use with general-purpose microprocessors
• Time of day/calendar
• Reads seconds, minutes, hours
• Reads day of month and month
• Alarm circuit with seconds, minutes or hours operation
• Power down mode
• Separate clock output selects 1 of 15 square wave signals
• Interrupt output activated by clock output and/or alarm circuit
• Data integrity sampling for clock rollover eliminated
• On-board oscillator 4.19 MHz, 2.09 MHz or 1.048 MHz
@ 10 V (CDP1879) crystal operation
4.19 MHz, 2.09 MHz, 1.048 MHz or 32 kHz @ 5 V
(CDP1879C-1) crystal operation
4.19 MHz, 2.09 MHz, 1.048 MHz or 32 kHz
@ 10 V or 5 V external clock operation
• Addressable in memory space or CDP1800 series I/O mode
• Low standby (timekeeping) voltage with external clock
The CDP1879 real-time clock supplies time and calendar
information from seconds to months in BCD format. It
consists of 5 separately addressable and programmable
counters that divide down an oscillator input. The clock
input can have anyone of 4 possible frequencies, allowing
flexibility in the choice of crystal or external clock sources.
Using an external 32-kHz clock source, timekeeping can be
performed down to 2.5 V (see Standby (Timekeeping)
Voltage Operation).
The device can be memory-mapped for use with any
general-purpose microprocessor and has the additional
capability of operating in the CDP1800-series input/output
mode.
The real-time clock functions as a time-of-day/calendar
with an alarm capability that can be set for combinations of
seconds, minutes or hours. Alarm time is configured by
loading alarm latches that activate an interrupt output
through a comparator when the counter and alarm latch
values are equal.
CDP1879 MODES OF OPERATION
OPERATION
FUNCTION
Fifteen selectable square-wave signals are available as a
separate clock output signal and can also activate the
interrupt output. A status register is available to indicate the
interrupt source. The value in an 8-bit control register
determines the operational characteristics of the device, by
selecting the prescaler divisor and the clock output, and
controls the load and alarm functions.
A transparent "freeze" circuit precludes clock rollover
during counter and latch access times to assure stable and
accurate values in the counters and alarm latches.
The CDP1879 is functionally identical to the CDP1879C-l.
The CDP1879 has a recommended operating voltage range
of 4 to 10.5 volts, and the CDP1879C-1 has a recommended
operating voltage range of 4 to 6.5 volts. The CDP1879 and
the CDP1879C-1 are supplied in 24-lead hermetic dual-in-
line side-brazed ceramic packages (0 suffix) and 24-lead
dual-in-line plastic packages (E suffix).
Read
1. Seconds, minutes, hours, date and month counters
2. Status register to identify interrupt source
Write
Power Down
Interrupt
1. Control register to set device operation
2. Seconds, minutes, hours, date and month counters
3. Alarm latches for alarm time
1. Tri-state interrupt output with active alarm or clock out circuitry for wake-up
control.
2. Data bus and address inputs are "DON'T CARE".
1. Clock out as source
2. Alarm time as source
3. Either ·interrupt can occur during normal or power down· mode
File Number 1360
452 ______________________________________________________________

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