M48T513YPM datasheet(3/23 Pages) STMICROELECTRONICS

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M48T513Y, M48T513V

Figure 3. Block Diagram

AI02584

LITHIUM

CELL

OSCILLATOR AND

CLOCK CHAIN

VPFD

VCC

VSS

32,768 Hz

CRYSTAL

VOLTAGE SENSE

AND

SWITCHING

CIRCUITRY

16 x 8

TIMEKEEPER

REGISTERS

524,272 x 8

SRAM ARRAY

A0-A18

DQ0-DQ7

POWER

RST

IRQ/FT

WDI

RSTIN

The unique design allows the SNAPHAT battery

package to be mounted on top of the SOIC pack-

age after the completion of the surface mount pro-

cess. Insertion of the SNAPHAT housing after

reflow prevents potential battery damage due to

the high temperatures required for device surface-

mounting. The SNAPHAT housing is keyed to pre-

vent reverse insertion.

The SNAPHAT battery package is shipped sepa-

rately in plastic anti-static tubes or in Tape & Reel

form. The part number is ”M4Txx-BR12SH1”.

Figure 3 illustrates the static memory array and the

quartz controlled clock oscillator. The clock loca-

tions contain the century, year, month, date, day,

hour, minute, and second in 24 hour BCD format.

Corrections for 28, 29 (leap year), 30, and 31 day

months are made automatically. The nine clock

bytes (7FFFFh-7FFF9h and 7FFF1h) are not the

actual clock counters, they are memory locations

consisting of BiPORT

™ read/write memory cells

within the static RAM array.

The M48T513Y/V includes a clock control circuit

which updates the clock bytes with current infor-

mation once per second. The information can be

accessed by the user in the same manner as any

other location in the static memory array. Byte

7FFF8h is the clock control register. This byte con-

trols user access to the clock information and also

stores the clock calibration setting.

Byte 7FFF7h contains the watchdog timer setting.

The watchdog timer can generate either a reset or

an interrupt, depending on the state of the Watch-

dog Steering bit (WDS). Bytes 7FFF6h-7FFF2h in-

clude bits that, when programmed, provide for

clock alarm functionality. Alarms are activated

when the register content matches the month,

date, hours, minutes, and seconds of the clock

registers. Byte 7FFF1h contains century informa-

tion. Byte 7FFF0h contains additional flag informa-

tion pertaining to the watchdog timer, the alarm

condition and the battery status. The M48T513Y/V

also has its own Power-Fail Detect circuit. This

control circuitry constantly monitors the supply

voltage for an out of tolerance condition. When

VCC is out of tolerance, the circuit write protects

the TIMEKEEPER register data and external

SRAM, providing data security in the midst of un-

predictable system operation. As VCC falls, the

control circuitry automatically switches to the bat-

tery, maintaining data and clock operation until

valid power is restored.

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