VT82887

Manufacturer Part NumberVT82887
ManufacturerETC-unknow
VT82887 datasheet
 


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VIA Technologies, Inc.
FEATURES
Drop-in replacement for IBM AT computer
clock/calendar.
Pin configuration closely matches the
DS12887
Totally nonvolatile with over 10 years of
operation in the absence of power
· Self-contained subsystem includes lithium,
quartz and support circuitry
Counts seconds, minutes, hours, days, day
of the week, date, month and year with leap
year compensation
Binary or BCD representation of time,
calendar and alarm
12- or 24-hour clock with AM and PM in 12-
hour mode
Daylight Savings Time option
Intel bus timing
Multiplex bus for pin efficiency
Interfaced with software as 128 RAM
locations
- 14 bytes of clock and control registers
- 114 bytes of general purpose RAM
Programmable square wave output signal
Bus-compatible interrupt signals (IRQ#)
Three interrupts are separately software-
maskable and testable
- Times-of-day alarm once/second to
once/day
- Periodic rates from 122 s to 500 ms
- End of clock update cycle
DESCRIPTION
The VT82887 Real Time Clock is designed to
be a direct replacement for the DS12887. The
VT82887 is identical in form, fit and function
to the DS12887. It has 114 bytes of general
purpose RAM. Access to this RAM space is
OPERATION
Real Time Clock
determined by the logic level presented on
AD6 during the address portion of an access
cycle. An external crystal and battery are the
only components required to maintain time-of-
day and memory status in the absence of
power. A complete description of operating
conditions,
electrical
characteristics,
timing and pin descriptions follows.
PIN ASSIGNMENT
VT82887 24 PIN DIP
GND
1
NC
2
NC
3
AD0
4
AD1
5
AD2
6
AD3
7
AD4
8
AD5
9
AD6
10
AD7
11
GND
12
PIN DESCRIPTION
AD0-AD7
- Multiplexed Address/Data Bus
NC
- No Connection
CS#
- Chip Select
AS
- Address Strobe
WR#
- Write Strobe
RD#
- Read Strobe
RESET#
- Reset Input
IRQ#
- Interrupt Request Output
SQW
- Square Wave Output
V
- +5 Volt Supply
CC
GND
- Ground
RCLR#
- RAM Clear
1
VT82887
bus
24
V
CC
23
SQW
22
NC
RCLR#
21
20
NC
19
IRQ#
18
RESET#
17
RD#
16
NC
15
WR#
14
AS
13
CS#

VT82887 Summary of contents