M48T58Y-70PC1FE 查看數據表（PDF） - STMicroelectronics

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M48T58Y-70PC1FE

5.0V, 64 Kbit (8 Kb x 8) TIMEKEEPER® SRAM

STMicroelectronics 

M48T58, M48T58Y

6

Clock operations

Clock operations

6.1

Reading the clock

Updates to the TIMEKEEPER® registers (see Table 5) should be halted before clock data is

read to prevent reading data in transition. The BiPORT™ TIMEKEEPER cells in the RAM

array are only data registers and not the actual clock counters, so updating the registers can

be halted without disturbing the clock itself.

Updating is halted when a '1' is written to the READ Bit, D6 in the Control Register 1FF8h.

As long as a '1' remains in that position, updating is halted.

After a halt is issued, the registers reflect the count; that is, the day, date, and the time that

were current at the moment the halt command was issued.

All of the TIMEKEEPER registers are updated simultaneously. A halt will not interrupt an

update in progress. Updating is within a second after the bit is reset to a '0.'

6.2

Setting the clock

Bit D7 of the Control register (1FF8h) is the WRITE Bit. Setting the WRITE Bit to a '1,' like

the READ Bit, halts updates to the TIMEKEEPER® registers. The user can then load them

with the correct day, date, and time data in 24 hour BCD format (see Table 5). Resetting the

WRITE Bit to a '0' then transfers the values of all time registers (1FF9h-1FFFh) to the actual

TIMEKEEPER counters and allows normal operation to resume. The bits marked as '0' in

Table 5 on page 16 must be written to '0' to allow for normal TIMEKEEPER and RAM

operation. After the WRITE Bit is reset, the next clock update will occur within one second.

See the Application Note AN923 “TIMEKEEPER Rolling Into the 21st Century” for

information on Century Rollover.

6.3

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 is the MSB of the seconds register. Setting it to a '1' stops the

oscillator. The M48T58/Y is shipped from STMicroelectronics with the STOP Bit set to a '1.'

When reset to a '0,' the M48T58/Y oscillator starts within 1 second.

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