M48T59 datasheet(9/21 Pages) STMICROELECTRONICS

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M48T59, M48T59Y, M48T59V

WRITE MODE

The M48T59/59Y/59V is in the Write Mode when-

ever W and E are low. The start of a write is refer-

enced from the latter occurring falling edge of W or

E. A write is terminated by the earlier rising edge

of W or E. The addresses must be held valid

throughout the cycle. E or W must return high for

a minimum of tEHAX from Chip Enable or tWHAX

from Write Enable prior to the initiation of another

read or write cycle. Data-in must be valid tDVWH

prior to the end of write and remain valid for tWHDX

afterward. G should be kept high during write cy-

cles to avoid bus contention; although, if the output

bus has been activated by a low on E and G a low

on W will disable the outputs tWLQZ after W falls.

DATA RETENTION MODE

With valid VCC applied, the M48T59/59Y/59V op-

erates as a conventional BYTEWIDE static RAM.

Should the supply voltage decay, the RAM will au-

tomatically power-fail deselect, write protecting it-

self when VCC falls within the VPFD (max), VPFD

(min) window. All outputs become high imped-

ance, and all inputs are treated as "don’t care."

Note: A power failure during a write cycle may cor-

rupt data at the currently addressed location, but

does not jeopardize the rest of the RAM’s content.

At voltages below VPFD (min), the user can be as-

sured the memory will be in a write protected state,

provided the VCC fall time is not less than tF. The

M48T59/59Y/59V may respond to transient noise

spikes on VCC that reach into the deselect window

Table 11. Register Map

Address

Data

Function/Range

BCD Format

1FFFh

10 Years

Year

00-99

1FFEh

10 M

Month

01-12

1FFDh

10 Date

Date

01-31

1FFCh

CEB

Day

Century/Day

00-01/01-07

1FFBh

10 Hours

Hours

Hour

00-23

1FFAh

10 Minutes

Minutes

00-59

1FF9h

10 Seconds

Seconds

00-59

1FF8h

Calibration

Control

1FF7h

WDS

BMB4

BMB3

BMB2

BMB1

BMB0

RB1

RB0

Watchdog

1FF6h

AFE

ABE

YYYYY

Interrupts

1FF5h

RPT4

Al. 10 Date

Alarm Date

01-31

1FF4h

RPT3

Al. 10 Hours

Alarm Hours

00-23

1FF3h

RPT2

Alarm 10 Minutes

Alarm Minutes

00-59

1FF2h

RPT1

Alarm 10 Seconds

Alarm Seconds

00-59

1FF1h

YYY

YYYYY

Unused

1FF0h

WDF

ZZZZ

Flags

Keys:

S = SIGN Bit

FT = FREQUENCY TEST Bit

R = READ Bit

W = WRITE Bit

ST = STOP Bit

0 = Must be set to zero

Y = ’1’ or ’0’

Z = ’0’ and are Read only

AF = Alarm Flag

BL = Battery Low

WDS = Watchdog Steering Bit

BMB0-BMB4 = Watchdog Multiplier Bits

RB0-RB1 = Watchdog Resolution Bits

AFE = Alarm Flag Enable

ABE = Alarm in Battery Back-up Mode Enable

RPT1-RPT4 = Alarm Repeat Mode Bits

WDF = Watchdog Flag

CEB = Century Enable Bit

CB = Century Bit

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