参数资料
| 型号： | SC900841JVKR2 |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 55/192页 |
| 文件大小： | 0K |
| 描述： | IC POWER MGT 338-MAPBGA |
| 标准包装： | 2,000 |
| 应用： | PC，PDA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 338-TFBGA |
| 供应商设备封装： | 338-MAPBGA |
| 包装： | 带卷 (TR) |
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FUNCTIONAL DEVICE OPERATION
CLOCK GENERATION AND REAL TIME CLOCK (RTC)
alarm bytes must use the same data mode, either binary or
BCD. Both the alarm hours, and the hours bytes must use the
same hours format, either 12 or 24.
The Set bit may now be cleared to allow updates. Once
initialized, the real-time clock makes all updates in the selected
data mode. The data mode (DM) cannot be changed without
re-initializing the 10 data bytes.
The 24/12 bit in Register B establishes whether the hour
locations represent 1-to-12 or 0-to-23. When the 12 hour
format is selected the high order bit of the hour bytes
represents PM when it is a "1". The 24/12 bit cannot be
changed without re-initializing the hour and alarm-hour
locations.
Table 23 shows the binary and BCD formats of the 10 time,
calendar, and alarm locations.
Table 23. Time, Calendar, and Alarm Data Modes
Address
location
Function
Decimal
Range
Binary Data Mode
Range
BCD Data Mode
Example (20)
Binary Data BCD Data
Mode Mode
0x10
0x11
0x12
0x13
Seconds
Seconds Alarm
Minutes
Minutes Alarm
0-59
0-59
0-59
0-59
$00-$3B
$00-$3B
$00-$3B
$00-$3B
$00-$59
$00-$59
$00-$59
$00-$59
15
15
3A
3A
21
21
58
58
0x14
Hours
0B
11
(12 Hour Mode)
(24 Hour Mode)
1-12
0-23
$01-$0C(AM) / $81-$92(PM)
$00-$17
$01-$12(AM) / $81-$92(PM)
$00-$23
0x15
Hours Alarm
0B
11
(12 Hour Mode)
(24 Hour Mode)
1-12
0-23
$01-$0C(AM) / $81-$92(PM)
$00-$17
$01-$12(AM) / $81-$92(PM)
$00-$23
0x16
Day of the Week
1-7
$01-$07
$01-$07
05
05
Sunday=1
0x17
0x18
0x19
Date of the Month
Month
Year
1-31
1-12
0-99
$01-$1F
$01-$0C
$00-$63
$01-$31
$01-$12
$00-$99
0F
02
08
15
02
08
Notes
20. Example: 11:58:21 Thursday 15 February 2008 (time is AM)
Reading the Time, Calendar, and Alarm
Under normal operation, the current time and date may be
read by accessing the RTC registers through the system SPI.
Since the alarm is only updated by a SPI write instruction, the
three alarm registers may be read at any time and will always
be defined.
The 900841 SPI will run at a minimum of 12.5 MHz. Each
individual SPI read transaction requires 25 cycles (less for
burst-read). The RTC contains seven timekeeping registers to
keep track of seconds, minutes, hours, day-of-week, day-of-
month, month, and year. If the SPI is clocked at the slowest
frequency, and the RTC is read using individual (not burst) SPI
read commands, the following equation gives the maximum
amount of time it takes the processor to read a complete date
and time (assuming the reads are done sequentially, and
uninterrupted): (25 * 7) / (12.5 MHz) = 14 μ s.
This equation shows that a program which randomly
accesses the time and date information will find the data in
transition statistically 14 times per million attempts. If a clock
update occurs during the time it takes to read all seven
timekeeping registers, the values read may be inconsistent. In
other words, if the program starts to read the seven date/time
registers and an RTC update occurs, the data collected may be
in transition. In this event, it is possible to read transition data
in one of the registers, resulting in undefined output. It is more
likely that the registers read after the update would be
incremented (by one second), and the registers read before the
update would not.
The time, calendar, and alarm bytes are always accessible
by the processor program. Once per second the seven bytes
are advanced by one second and checked for an alarm
condition. If any of the seven bytes are read at this time, the
data outputs should be considered undefined. Similarly, all
seven bytes should be read between updates to get a
consistent time and date. Reading some of the bytes before an
update and some after, may result in an erroneous output. The
update cycle in the processor program.
Update Cycle
The RTC module executes an update cycle once per
second, assuming one of the proper time bases is in place and
900841
Analog Integrated Circuit Device Data
Freescale Semiconductor
55
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