M48T251VPM datasheet(4/24 Pages) STMICROELECTRONICS

4 / 24 page

M48T251Y, M48T251V

4/24

SUMMARY DESCRIPTION

The M48T251Y/V TIMEKEEPER® RAM is a

512Kbit x 8 non-volatile static RAM and real time

clock organized as 524,288 words by 8 bits. The

special DIP package provides a fully integrated

battery back-up memory and real time clock solu-

tion. In the event of power instability or absence, a

self-contained battery maintains the timekeeping

operation and provides power for a CMOS static

RAM. Control circuitry monitors VCC and invokes

write protection to prevent data corruption in the

memory and RTC.

The clock keeps track of tenths/hundredths of sec-

onds, seconds, minutes, hours, day, date, month,

and year information. The last day of the month is

automatically adjusted for months with less than

31 days, including leap year correction.

The clock operates in one of two formats:

–

a 12-hour mode with an AM/PM indicator;

–

a 24-hour mode

The M48T251Y/V is a 32-pin (PM) DIP module

that integrates the RTC, the battery, and SRAM in

one package.

The modules are shipped in plastic, anti-static

tubes (see Table 14., page 22).

Figure 2. Logic Diagram

Table 1. Signal Names

A0-A18

VSS

DQ0-D7

M48T251Y

M48T251V

VCC

RST

AI04237

A0–A18

Address Input

RST

Reset Input

Chip Enable

Output Enable Input

WRITE Enable Input

DQ0–DQ7

Data Inputs/Outputs

VCC

Supply Voltage Input

VSS

Ground

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