M41T00S datasheet(10/23 Pages) STMICROELECTRONICS

10 / 23 page

M41T00S

10/23

WRITE Mode

In this mode the master transmitter transmits to

the M41T00S slave receiver. Bus protocol is

shown in Figure 10. Following the START condi-

tion and slave address, a logic '0' (R/W=0) is

placed on the bus and indicates to the addressed

device that word address “An” will follow and is to

be written to the on-chip address pointer. The data

word to be written to the memory is strobed in next

and the internal address pointer is incremented to

the next address location on the reception of an

acknowledge clock. The M41T00S slave receiver

will send an acknowledge clock to the master

transmitter after it has received the slave address

see Figure 7., page 8 and again after it has re-

ceived the word address and each data byte.

Data Retention Mode

With valid VCC applied, the M41T00S can be ac-

cessed as described above with READ or WRITE

Cycles. Should the supply voltage decay, the pow-

er input will be switched from the VCC pin to the

battery when VCC falls below the Battery Back-up

Switchover Voltage (VSO). At this time the clock

registers will be maintained by the attached bat-

tery supply. On power-up, when VCC returns to a

nominal value, write protection continues for tREC.

For a further, more detailed review of lifetime cal-

culations, please see Application Note AN1012.

Figure 10. WRITE Mode Sequence

AI00591

BUS ACTIVITY:

SDA LINE

BUS ACTIVITY:

MASTER

DATA n

DATA n+1

DATA n+X

WORD

ADDRESS (An)

SLAVE

ADDRESS

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