Operation

M41T81

8/30

2

Operation

The M41T81 clock operates as a slave device on the serial bus. Access is obtained by

implementing a start condition followed by the correct slave address (D0h). The 20 bytes

contained in the device can then be accessed sequentially in the following order:

●

●

●

●

●

●

●

●

●

●

●

●

●

counter. Inputs to the device will not be recognized at this time to prevent erroneous data

from being written to the device from a an out-of-tolerance system. The device also

automatically switches over to the battery and powers down into an ultra low current mode

For more information on Battery Storage Life refer to Application Note AN1012.

2.1

2-wire bus characteristics

The bus is intended for communication between different ICs. It consists of two lines: a bi-

directional data signal (SDA) and a clock signal (SCL). Both the SDA and SCL lines must be

connected to a positive supply voltage via a pull-up resistor.

The following protocol has been defined:

●

Data transfer may be initiated only when the bus is not busy.

●

During data transfer, the data line must remain stable whenever the clock line is High.

●

Changes in the data line, while the clock line is High, will be interpreted as control

signals.

Accordingly, the following bus conditions have been defined:

2.1.1

Bus not busy

Both data and clock lines remain High.