M48T02, M48T12

6/19

Table 5. DC Characteristics

2. Outputs deselected.

3. Measured with Control Bits set as follows: R = '1'; W, ST, FT = '0.'

4. Negative spikes of –1V allowed for up to 10ns once per Cycle.

OPERATION MODES

As Figure 4, page 4 shows, the static memory ar-

ray and the quartz controlled clock oscillator of the

M48T02/12 are integrated on one silicon chip. The

two circuits are interconnected at the upper eight

memory locations to provide user accessible

BYTEWIDE™ clock information in the bytes with

addresses 7F8h-7FFh. The clock locations con-

tain the year, month, date, day, hour, minute, and

second in 24 hour BCD format. Corrections for 28,

29 (leap year - valid until 2100), 30, and 31 day

months are made automatically.

Byte 7F8h is the clock control register. This byte

controls user access to the clock information and

also stores the clock calibration setting.

The eight clock bytes are not the actual clock

counters themselves; they are memory locations

consisting of BiPORT™ READ/WRITE memory

cells. The M48T02/12 includes a clock control cir-

cuit which updates the clock bytes with current in-

formation once per second. The information can

be accessed by the user in the same manner as

any other location in the static memory array.

The M48T02/12 also has its own Power-fail Detect

circuit. The control circuitry constantly monitors

the single 5V supply for an out of tolerance condi-

protects the SRAM, providing a high degree of

data security in the midst of unpredictable system

low approximately 3V, the control circuitry con-

nects the battery which maintains data and clock

operation until valid power returns.

Table 6. Operating Modes

1. See Table 10, page 11 for details.

Symbol

Parameter

Min

Max

Unit

Input Leakage Current

0V

±1

µA

(2)

Output Leakage Current

0V

±1

µA

Supply Current

Outputs open

80

mA

(3)

Supply Current (Standby) TTL

3mA

(3)

Supply Current (Standby) CMOS

3mA

(4)

Input Low Voltage

–0.3

0.8

V

Input High Voltage

2.2

V

Output Low Voltage

0.4

V

Output High Voltage

2.4

V

Mode

E

G

W

DQ0-DQ7

Power

Deselect

4.75 to 5.5V

or

4.5 to 5.5V

X

X

High Z

Standby

WRITE

X

Active

READ

Active

READ

High Z

Active

Deselect

(1)

X

X

X

High Z

CMOS Standby

Deselect

X

X

X

High Z

Battery Back-up Mode