参数资料
型号: M41ST87WMX6TR
厂商: STMICROELECTRONICS
元件分类: 时钟/数据恢复及定时提取
英文描述: 1 TIMER(S), REAL TIME CLOCK, PDSO28
封装: 0.300 INCH, ROHS COMPLIANT, PLASTIC, SOX-28
文件页数: 31/48页
文件大小: 457K
代理商: M41ST87WMX6TR
M41ST87Y, M41ST87W
Clock operation
output will be configured as open drain (with IOL as specified in Table 17 on page 42). When
PFOD is set to '0,' the outputs will be configured as full-CMOS (sink and source current as
Note:
When configured as open drain (PFOD = '1'), PFO1 and PFO2 will require an external pull-
up resistor.
3.11
Century bits
These two bits will increment in a binary fashion at the turn of the century, and handle leap
years correctly. See Table 11 on page 38 for additional explanation.
3.12
Output driver pin
When the TIE bit, OFIE bit, AFE bit, and watchdog register are not set to generate an
interrupt, the IRQ/OUT pin becomes an output driver that reflects the contents of D7 of the
control register. In other words, when D7 (OUT Bit) is a '0,' then the IRQ/OUT pin will be
driven low. With the ABE bit set to '1,' the OUT pin will continue to be driven low in battery
backup.
Note:
The IRQ/OUT pin is an open drain which requires an external pull-up resistor.
3.13
Battery low warning
The M41ST87Y/W automatically performs battery voltage monitoring upon power-up and at
factory-programmed time intervals of approximately 24 hours. The battery low (BL) bit, bit
D4 of flags register 0Fh, will be asserted if the battery voltage is found to be less than
approximately 2.5 V. The BL bit will remain asserted until completion of battery replacement
and subsequent battery low monitoring tests, either during the next power-up sequence or
the next scheduled 24-hour interval.
If a battery low is generated during a power-up sequence, this indicates that the battery is
below approximately 2.5 volts and may not be able to maintain data integrity in the SRAM.
Data should be considered suspect and verified as correct. A fresh battery should be
installed.
If a battery low indication is generated during the 24-hour interval check, this indicates that
the battery is near end of life. However, data is not compromised due to the fact that a
nominal VCC is supplied. In order to insure data integrity during subsequent periods of
battery back-up mode, the battery should be replaced. The battery may be replaced while
VCC is applied to the device.
The M41ST87Y/W only monitors the battery when a nominal VCC is applied to the device.
Thus applications which require extensive durations in the battery back-up mode should be
powered-up periodically (at least once every few months) in order for this technique to be
beneficial. Additionally, if a battery low is indicated, data integrity should be verified upon
power-up via a checksum or other technique.
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