M48Z2M1 datasheet(7/12 Pages) STMICROELECTRONICS

7 / 12 page

AI02052

tAVAV

tAVQV

tAXQX

tELQV

tELQX

tEHQZ

tGLQV

tGLQX

tGHQZ

DATA OUT

A0-A20

DQ0-DQ7

VALID

Figure 7. Chip Enable or Output Enable Controlled, Read Mode AC Waveforms

Note: Write Enable (W) = High.

DATA RETENTION MODE

With valid VCC applied, the M48Z2M1/2M1Y oper-

ates as a conventional BYTEWIDE

™ static RAM.

Should the supply voltage decay, the RAM will

automatically power-fail deselect, write protecting

itself tWP after VCC falls below VPFD. All outputs

become high impedance, and all inputs are treated

as "don’t care."

If power fail detection occurs during a valid access,

the memory cycle continues to completion. If the

memory cycle fails to terminate within the time tWP,

write protection takes place. When VCC drops be-

low VSO, the control circuit switches power to the

internal energy source which preserves data.

The internal coin cells will maintain data in the

M48Z2M1/2M1Y after the initial application of VCC

for an accumulated period of at least 10 years when

VCC is less than VSO. As system power returns and

VCC rises above VSO, the batteries are discon-

nected, and the power supply is switched to exter-

nal Vcc. Write protection continues for tER after VCC

reaches VPFD to allow for processor stabilization.

After tER, normal RAM operation can resume.

For more information on Battery Storage life refer

to the Application Note AN1012.

7/12

M48Z2M1, M48Z2M1Y

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