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VT82887 Datasheet(PDF) 2 Page - List of Unclassifed Manufacturers

Part No. VT82887
Description  Real Time Clock
Download  17 Pages
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Maker  ETC1 [List of Unclassifed Manufacturers]
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VT82887 Datasheet(HTML) 2 Page - List of Unclassifed Manufacturers

 
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VT82887
Real Time Clock
VIA Technologies, Inc.
The block diagram in Figure 1 shows the
pin connections with the major internal functions
of the VT82887. The following paragraphs
describe the function of each pin.
FIGURE 1: BLOCK DIAGRAM VT82887
POWER-DOWN/POWER-UP
CONSIDERATIONS
The Real Time Clock function will continue to
operate and all of the RAM, time, calendar
and
alarm
memory
locations
remain
nonvolatile regardless of the level of the VCC
input. When VCC is applied to the VT82887
and reaches a level of greater than 4.25 volts,
the device becomes accessible after 100 ms,
provided that the oscillator is running and the
oscillator countdown chain is not in reset (see
Register A). This time period allows the
system to stabilize after power is applied.
When VCC falls below 4.25 volts, the chip
select input is internally forced to an inactive
level regardless of the value of CS# at the
input pin. The VT82887 is, therefore, write-
protected. When VCC falls below the level of
VBAT, the external VCC supply is switched off
and the external VBAT lithium energy source
supplies power to the Real Time Clock and
the RAM memory.
OSC
8
64
64
PERIODIC INTERUPT SQUARE WAVE
SELECTOR
SQUARE
WAVE OUT
POWER
SWITCH
AND
WRITE
PROTECT
BUS
INTERFACE
CLOCK/
CALENDAR
UPDATE
BCD/
BINARY
INCREMENT
REGISTERS A,B,C,D
CLOCK, CALENDAR
AND ALARM RAM
USER RAM
114 BYTES
AS
RD#
AD0-
AD7
WR#
VBAT
VCC
CS#
CS#
SQW
IRQ#
RESET#
RCLR#
PWGD
VCC
DOUBLE
BUFFERED


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