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參數資料
| 型號： | M48TMH1TR |
| 廠商： | 意法半導體 |
| 英文描述： | 5V PC REAL TIME CLOCK |
| 中文描述： | 5V的電腦實時時鐘 |
| 文件頁數： | 6/23頁 |
| 文件大?。?/td> | 163K |
| 代理商： | M48TMH1TR |
M48T86
6/23
Table 3. Time, Calendar and Alarm Formats
Address
RTC Bytes
Range
Decimal
Binary
BCD
0
Seconds
0-59
00-3B
00-59
1
Seconds Alarm
0-59
00-3B
00-59
2
Minutes
0-59
00-3B
00-59
3
Minutes Alarm
0-59
00-3B
00-59
4
Hours, 12-hrs
1-12
01-0C AM
81-8C PM
01-12 AM
81-92 PM
Hours, 24-hrs
0-23
00-17
00-23
5
Hours Alarm, 12-hrs
1-12
01-0C AM
81-8C PM
01-12 AM
81-92 PM
Hours Alarm, 24-hrs
0-23
00-17
00-23
6
Day of Week (1 = Sun)
1-7
01-07
01-07
7
Day of Month
1-31
01-1F
01-31
8
Month
1-12
01-0C
01-12
9
Year
0-99
00-63
00-99
TIME, CALENDAR, AND ALARM LOCATIONS
The time and calendar information is obtained by
reading the appropriate memory bytes. The time,
calendar, and alarm registers are set or initialized
by writing the appropriate RAM bytes. The con-
tents of the time, calendar, and alarm bytes can be
either Binary or Binary-Coded Decimal (BCD) for-
mat. Before writing the internal time, calendar, and
alarm register, the SET bit (Register B; Bit 7)
should be written to a logic "1". This will prevent
updates from occurring while access is being at-
tempted. In addition to writing the time, calendar,
and alarm registers in a selected format (binary or
BCD), the Data Mode (DM) bit (Register B; Bit 2),
must be set to the appropriate logic level ("1" sig-
nifies binary data; "0" signifies Binary Coded Dec-
imal (BCD data). All time, calendar, and alarm
bytes must use the same data mode. The SET bit
should be cleared after the Data Mode bit has
been written to allow the Real Time Clock to up-
date the time and calendar bytes. Once initialized,
the Real Time Clock makes all updates in the se-
lected mode. The data mode cannot be changed
without reinitializing the ten data bytes. Table 3
shows the binary and BCD formats of the time, cal-
endar, and alarm locations. The 24/12 bit (Regis-
ter B; Bit 1) cannot be changed without
reinitializing the hour locations. When the 12-hour
format is selected, a logic one in the high order bit
of the hours byte represents PM. The time, calen-
dar, and alarm bytes are always accessible be-
cause they are double buffered. Once per second
the ten bytes are advanced by one second and
checked for an alarm condition. If a read of the
time and calendar data occurs during an update, a
problem exists where seconds, minutes, hours,
etc. may not correlate. However, the probability of
reading incorrect time and calendar data is low.
Methods of avoiding possible incorrect time and
calendar reads are reviewed later in this text.
NON-VOLATILE RAM
The 114 general purpose non-volatile RAM bytes
are not dedicated to any special function within the
M48T86. They can be used by the processor pro-
gram as non-volatile memory and are fully acces-
sible during the update cycle.
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