m41t64 STMicroelectronics, m41t64 Datasheet - Page 8

• Manufacturer Part Number: m41t64
• Description: Serial Access Real-time Clock With Alarms
• Manufacturer: STMicroelectronics

M41T62/63/64/65
OPERATION
The M41T6x clock operates as a slave device on
the serial bus. Access is obtained by implementing
a start condition followed by the correct slave ad-
dress (D0h). The 16 bytes contained in the device
can then be accessed sequentially in the following
order:
1. Tenths/Hundredths of a Second Register
2. Seconds Register
3. Minutes Register
4. Hours Register
5. Square Wave/Day Register
6. Date Register
7. Century/Month Register
8. Year Register
9. Calibration Register
10. Watchdog Register
11 - 15. Alarm Registers
16. Flags Register
2-Wire Bus Characteristics
The bus is intended for communication between
different ICs. It consists of two lines: a bi-direction-
al 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:
–
–
–
8/33
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:
Bus not busy. Both data and clock lines remain
High.
Start data transfer. A change in the state of the
data line, from high to Low, while the clock is High,
defines the START condition.
Stop data transfer. A change in the state of the
data line, from Low to High, while the clock is High,
defines the STOP condition.
Data Valid. The state of the data line represents
valid data when after a start condition, the data line
is stable for the duration of the high period of the
clock signal. The data on the line may be changed
during the Low period of the clock signal. There is
one clock pulse per bit of data.
Each data transfer is initiated with a start condition
and terminated with a stop condition. The number
of data bytes transferred between the start and
stop conditions is not limited. The information is
transmitted byte-wide and each receiver acknowl-
edges with a ninth bit.
By definition a device that gives out a message is
called “transmitter,” the receiving device that gets
the message is called “receiver.” The device that
controls the message is called “master.” The de-
vices that are controlled by the master are called
“slaves.”