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參數(shù)資料
| 型號： | DS17487B-3 |
| 英文描述： | 3V/5V Real-Time Clock |
| 中文描述： | 3V/5V實(shí)時時鐘 |
| 文件頁數(shù)： | 15/38頁 |
| 文件大?。?/td> | 427K |
| 代理商： | DS17487B-3 |
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DS17485/DS17487
15 of 38
UPDATE CYCLE
The serialized RTC executes an update cycle once per second regardless of the SET bit in Register B.
When the SET bit in Register B is set to 1, the user copy of the double-buffered time, calendar, alarm,
and elapsed time byte is frozen and does not update as the time increments. However, the time countdown
chain continues to update the internal copy of the buffer. This feature allows the time to maintain
accuracy independent of reading or writing the time, calendar, and alarm buffers and also guarantees that
time and calendar information is consistent. The update cycle also compares each alarm byte with the
corresponding time byte and issues an alarm if a match or if a “don’t care” code is present in all alarm
locations.
There are three methods that can handle access of the RTC that avoid any possibility of accessing
inconsistent time and calendar data. The first method uses the update-ended interrupt. If enabled, an
interrupt occurs after every update cycle that indicates that over 999ms is available to read valid time and
date information. If this interrupt is used, the IRQF bit in Register C should be cleared before leaving the
interrupt routine.
A second method uses the update-in-progress bit (UIP) in Register A to determine if the update cycle is in
progress. The UIP bit pulses once per second. After the UIP bit goes high, the update transfer occurs
244μs later. If a low is read on the UIP bit, the user has at least 244μs before the time/calendar data is
changed. Therefore, the user should avoid interrupt service routines that would cause the time needed to
read valid time/calendar data to exceed 244μs.
The third method uses a periodic interrupt to determine if an update cycle is in progress. The UIP bit in
Register A is set high between the setting of the PF bit in Register C (Figure 3). Periodic interrupts that
occur at a rate of greater than t
BUC
allow valid time and date information to be reached at each occurrence
of the periodic interrupt. The reads should be complete within (t
PI
/ 2 + t
BUC
) to ensure that data is not
read during the update cycle.
Figure 3. UPDATE-ENDED AND PERIODIC INTERRUPT RELATIONSHIP
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| DS17487B-5 | 3V/5V Real-Time Clock |
| DS17487BN-3 | 3V/5V Real-Time Clock |
| DS17487BN-5 | 3V/5V Real-Time Clock |
| DS17487N-3 | 3V/5V Real-Time Clock |
| DS17487N-5 | 49.9 1% 1/4W 1206 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS17487B-5 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:3V/5V Real-Time Clock |
| DS17487BN-3 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:3V/5V Real-Time Clock |
| DS17487BN-5 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:3V/5V Real-Time Clock |
| DS17487N-3 | 功能描述:IC RTC 3V 4K NV RAM 24-EDIP RoHS:否 類別:集成電路 (IC) >> 時鐘/計(jì)時 - 實(shí)時時鐘 系列:- 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- 類型:時鐘/日歷 特點(diǎn):警報器，閏年，SRAM 存儲容量:- 時間格式:HH:MM:SS（12/24 小時） 數(shù)據(jù)格式:YY-MM-DD-dd 接口:SPI 電源電壓:2 V ~ 5.5 V 電壓 - 電源，電池:- 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-WDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:8-TDFN EP 包裝:管件 |
| DS17487N-5 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:3V/5V Real-Time Clock |
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