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參數(shù)資料
| 型號： | M48T18-150PC1 |
| 廠商： | STMICROELECTRONICS |
| 元件分類： | 時鐘/數(shù)據(jù)恢復及定時提取 |
| 英文描述： | 0 TIMER(S), REAL TIME CLOCK, PDIP28 |
| 封裝： | 0.600 INCH, ROHS COMPLIANT, PLASTIC, PCDIP-28 |
| 文件頁數(shù)： | 7/31頁 |
| 文件大?。?/td> | 256K |
| 代理商： | M48T18-150PC1 |
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M48T08, M48T08Y, M48T18
Clock operations
Table 5.
Register map
Note:
S = SIGN bit
FT = FREQUENCY TEST bit (set to '0' for normal clock operation)
R = READ bit
W = WRITE bit
ST = STOP bit
0 = Must be set to '0'
3.3
Stopping and starting the oscillator
The oscillator may be stopped at any time. If the device is going to spend a significant
amount of time on the shelf, the oscillator can be turned off to minimize current drain on the
battery. The STOP bit (ST) is the MSB of the seconds register. Setting it to a '1' stops the
oscillator. The M48T08/18/08Y (in the PCDIP28 package) is shipped from
STMicroelectronics with the STOP bit set to a '1.' When reset to a '0,' the M48T08/18/08Y
oscillator starts within one second.
Note:
To guarantee oscillator startup after initial power-up, first write the STOP bit (ST) to '1,' then
reset to '0.'
3.4
Calibrating the clock
The M48T08/18/08Y is driven by a quartz-controlled oscillator with a nominal frequency of
32,768 Hz. A typical M48T08/18/08Y is accurate within 1 minute per month at 25°C without
calibration. The devices are tested not to exceed ± 35 ppm (parts per million) oscillator
frequency error at 25°C, which equates to about ±1.53 minutes per month. With the
calibration bits properly set, the accuracy of each M48T08/18/08Y improves to better than
+1/–2 ppm at 25°C.
The oscillation rate of any crystal changes with temperature. Figure 8 on page 17 shows the
frequency error that can be expected at various temperatures. Most clock chips compensate
for crystal frequency and temperature shift error with cumbersome “trim” capacitors. The
M48T08/18/08Y design, however, employs periodic counter correction. The calibration
circuit adds or subtracts counts from the oscillator divider circuit at the divide by 256 stage,
as shown in Figure 9 on page 17. The number of times pulses are blanked (subtracted,
negative calibration) or split (added, positive calibration) depends upon the value loaded into
Address
Data
Function/range
BCD format
D7
D6
D5
D4
D3
D2
D1
D0
1FFFh
10 years
Year
00-99
1FFEh
0
10 M
Month
01-12
1FFDh
0
10 date
Date
01-31
1FFCh
0
FT
0
Day
01-07
1FFBh
0
10 hours
Hours
00-23
1FFAh
0
10 minutes
Minutes
00-59
1FF9h
ST
10 seconds
Seconds
00-59
1FF8h
W
R
S
Calibration
Control
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| M48T18-150PC1E | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:64 Kbit 8Kb x 8 TIMEKEEPER SRAM |
| M48T18-150PC1F | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:64 Kbit 8Kb x 8 TIMEKEEPER SRAM |
| M48T18-150PC1TR | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:CMOS 8K x 8 TIMEKEEPER SRAM |
| M48T18MH | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:64 Kbit 8Kb x 8 TIMEKEEPER SRAM |
| M48T18PC | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:64 Kbit 8Kb x 8 TIMEKEEPER SRAM |
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