M41T11 Description
Doc ID 6103 Rev 10 7/30
Figure 4. Block diagram
AI02566
SECONDS
OSCILLATOR
32.768 kHz
VOLTAGE
SENSE
and
SWITCH
CIRCUITRY
SERIAL
BUS
INTERFACE
DIVIDER
CONTROL
LOGIC
ADDRESS
REGISTER
MINUTES
CENTURY/HOURS
DAY
DATE
MONTH
YEAR
CONTROL
RAM
(56 x 8)
OSCI
OSCO
FT/OUT
V
CC
V
SS
V
BAT
SCL
SDA
1 Hz
Operation M41T11
8/30 Doc ID 6103 Rev 10
2 Operation
The M41T11 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 64 bytes
contained in the device can then be accessed sequentially in the following order:
1
st
byte: seconds register
2
nd
byte: minutes register
3
rd
byte: century/hours register
4
th
byte: day register
5
th
byte: date register
6
th
byte: month register
7
th
byte: years register
8
th
byte: control register
9
th
- 64
th
bytes: RAM
The M41T11 clock continually monitors V
CC
for an out of tolerance condition. Should V
CC
fall below V
SO
, the device terminates an access in progress and resets the device address
counter. Inputs to the device will not be recognized at this time to prevent erroneous data
from being written to the device from an out of tolerance system. When V
CC
falls below V
SO
,
the device automatically switches over to the battery and powers down into an ultra low
current mode of operation to conserve battery life. Upon power-up, the device switches from
battery to V
CC
at V
SO
and recognizes inputs.
2.1 2-wire bus characteristics
This bus is intended for communication between different ICs. It consists of two lines: one
bidirectional for data signals (SDA) and one for clock signals (SCL). Both the SDA and the
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.
2.1.2 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.
M41T11 Operation
Doc ID 6103 Rev 10 9/30
2.1.3 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.
2.1.4 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 acknowledges 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 devices that are controlled by the master are called “slaves”.
2.1.5 Acknowledge
Each byte of eight bits is followed by one acknowledge bit. This acknowledge bit is a low
level put on the bus by the receiver, whereas the master generates an extra acknowledge
related clock pulse.
A slave receiver which is addressed is obliged to generate an acknowledge after the
reception of each byte. Also, a master receiver must generate an acknowledge after the
reception of each byte that has been clocked out of the slave transmitter.
The device that acknowledges has to pull down the SDA line during the acknowledge clock
pulse in such a way that the SDA line is a stable low during the high period of the
acknowledge related clock pulse. Of course, setup and hold times must be taken into
account. A master receiver must signal an end-of-data to the slave transmitter by not
generating an acknowledge on the last byte that has been clocked out of the slave. In this
case, the transmitter must leave the data line high to enable the master to generate the
STOP condition.
Figure 5. Serial bus data transfer sequence
AI00587
DATA
CLOCK
DATA LINE
STABLE
DATA VALID
START
CONDITION
CHANGE OF
DATA ALLOWED
STOP
CONDITION

M41T11M6F

Mfr. #:
Manufacturer:
STMicroelectronics
Description:
Real Time Clock Serial 512 (64x8)
Lifecycle:
New from this manufacturer.
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