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VT82887 Datasheet(PDF) 5 Page - List of Unclassifed Manufacturers

Part No. VT82887
Description  Real Time Clock
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Maker  ETC1 [List of Unclassifed Manufacturers]
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VT82887 Datasheet(HTML) 5 Page - List of Unclassifed Manufacturers

 
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5
VT82887
Real Time Clock
VIA Technologies, Inc.
contain the RTC time, calendar and alarm
data, and four bytes which are used for
control and status. All 128 bytes can be
directly
written
or
read
except
for
the
following:
1.
Registers C and D are read-only.
2.
Bit 7 of Register A is read-only.
3.
The high order bit of the seconds byte is
read-only.
The contents of four registers (A, B, C and D)
are described in the “Register” section.
FIGURE 2: ADDRESS MAP VT82887
TIME, CALENDAR AND ALARM
LOCATIONS
The time and calendar information is obtained
by reading the appropriate memory bytes.
The
time,
calendar
and
alarm
are
set
or initialized by writing the appropriate RAM
bytes. The contents of the ten time, calendar
and alarm bytes can be either Binary or
Binary-Coded Decimal (BCD) format. Before
writing the internal time, calendar and alarm
registers, the SET bit in Register B should be
written to a logic one to prevent updates from
occurring while access is being attempted. In
addition to writing the ten time, calendar and
alarm registers in a selected format (binary or
BCD), the data mode bit (DM) of Register B
must be set to the appropriate logic level. All
ten time, calendar and alarm bytes must use
the same data mode. The SET bit in Register
B should be cleared after time, calendar or
alarm have been written to allow the real time
clock to update the time and calendar bytes.
Once initialized, the real time clock makes all
updates in the selected mode. The data mode
cannot be changed without reinitializing the
ten data bytes. Table 2 shows the binary and
BCD formats of the ten time, calendar and
alarm locations. The 24-12 bit cannot be
changed
without
reinitializing
the
hour
locations.
When
the
12-hour
format
is
selected, the high order bit of the hours byte
0
SECONDS
00
1
SECONDS ALARM
01
2
MINUTES
02
3
MINUTES ALARM
03
4
HOURS
04
5
HOURS ALARM
05
6
DAY OF THE WEEK
06
7
DAY OF THE MONTH
07
8
MONTH
08
9
YEAR
09
10
REGISTER A
0A
11
REGISTER B
0B
12
REGISTER C
0C
13
REGISTER D
0D
127
0
00
OD
0E
13
14
7F
14 Bytes
Clock and Control
Status Registers
114 Bytes
Storage
Registers
Binary or BCD Input


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