M41T00 ,SERIAL ACCESS TIMEKEEPERFEATURES SUMMARY
M41T00
SERIAL ACCESS TIMEKEEPER
1/20November 2002
M41T00SERIAL ACCESS TIMEKEEPER®
FEATURES SUMMARY 2.0 TO 5.5V CLOCK OPERATING VOLTAGE COUNTERS FOR SECONDS, MINUTES,
HOURS, DAY, DATE, MONTH, YEARS, and
CENTURY YEAR 2000 COMPLIANT SOFTWARE CLOCK CALIBRATION AUTOMATIC SWITCH-OVER and DESELECT
CIRCUITRYI2 C BUS COMPATIBLE ULTRA-LOW BATTERY SUPPLY CURRENT
OF 1μA LOW OPERATING CURRENT OF 300μA BATTERY OR SUPER-CAP BACK-UP BATTERY BACK-UP NOT RECOMMENDED
FOR 3.0V APPLICATIONS (CAPACITOR
BACK-UP ONLY) OPERATING TEMPERATURE OF –40 TO
85°C AUTOMATIC LEAP YEAR COMPENSATION SPECIAL SOFTWARE PROGRAMMABLE
OUTPUT
Figure 1. 8-pin SOIC Package
M41T00
TABLE OF CONTENTS
SUMMARY DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Logic Diagram (Figure 2.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
SOIC Connections (Figure 3.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Signal Names (Table 1.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Block Diagram (Figure 4.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
MAXIMUM RATING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Absolute Maximum Ratings (Table 2.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
DC AND AC PARAMETERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Operating and AC Measurement Conditions (Table 3.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
AC Testing Input/Output Waveform (Figure 5.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Capacitance (Table 4.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
DC Characteristics (Table 5.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Crystal Electrical Characteristics (Table 6.). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82-Wire Bus Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Serial Bus Data Transfer Sequence (Figure 6.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Acknowledgement Sequence (Figure 7.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Bus Timing Requirements Sequence (Figure 8.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
AC Characteristics (Table 7.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
READ Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
WRITE Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Slave Address Location (Figure 9.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
READ Mode Sequence (Figure 10.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Alternate READ Mode Sequence (Figure 11.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
WRITE Mode Sequence (Figure 12.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Data Retention Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Power Down/Up Mode AC Waveforms (Figure 13.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Power Down/Up AC Characteristics (Table 8.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Power Down/Up Trip Points DC Characteristics (Table 9.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
CLOCK OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14Register Map (Table 10.). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Clock Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Output Driver Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Initial Power-on Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Crystal Accuracy Across Temperature (Figure 14.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Clock Calibration (Figure 15.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
PART NUMBERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
PACKAGE MECHANICAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
REVISION HISTORY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
3/20
M41T00
SUMMARY DESCRIPTIONThe M41T00 TIMEKEEPER® RAM is a low power
Serial TIMEKEEPER with a built-in 32.768kHz os-
cillator (external crystal controlled). Eight bytes of
the RAM are used for the clock/calendar function
and are configured in binary coded decimal (BCD)
format. Addresses and data are transferred serial-
ly via a two-line bi-directional bus. The built-in ad-
dress register is incremented automatically after
each WRITE or READ data byte.
The M41T00 clock has a built-in power sense cir-
cuit which detects power failures and automatical-
ly switches to the battery supply during power
failures. The energy needed to sustain the RAM
and clock operations can be supplied from a small
lithium coin cell.
Typical data retention time is in excess of 5 years
with a 50mA/h 3V lithium cell (see Data Retention
Mode, page 13 for AC/DC Characteristics). The
M41T00 is supplied in 8 lead Plastic Small Outline
package.
Figure 2. Logic Diagram
Figure 3. SOIC Connections
Table 1. Signal Names
M41T00
Figure 4. Block Diagram
5/20
M41T00
MAXIMUM RATINGStressing the device above the rating listed in the
“Absolute Maximum Ratings” table may cause
permanent damage to the device. These are
stress ratings only and operation of the device at
these or any other conditions above those indicat-
ed in the Operating sections of this specification is
not implied. Exposure to Absolute Maximum Rat-
ing conditions for extended periods may affect de-
vice reliability. Refer also to the
STMicroelectronics SURE Program and other rel-
evant quality documents.
Table 2. Absolute Maximum RatingsNote:1. Reflow at peak temperature of 215°C to 225°C for < 60 seconds (total thermal budget not to exceed 180°C for between 90 and 120
seconds).
CAUTION: Negative undershoots below –0.3V are not allowed on any pin while in the Battery Back-up mode.
M41T00
DC AND AC PARAMETERSThis section summarizes the operating and mea-
surement conditions, as well as the DC and AC
characteristics of the device. The parameters in
the following DC and AC Characteristic tables are
derived from tests performed under the Measure-
ment Conditions listed in the relevant tables. De-
signers should check that the operating conditions
in their projects match the measurement condi-
tions when using the quoted parameters.
Table 3. Operating and AC Measurement ConditionsNote: Output Hi-Z is defined as the point where data is no longer driven.
Figure 5. AC Testing Input/Output Waveform
Table 4. CapacitanceNote:1. Effective capacitance measured with power supply at 5V; sampled only, not 100% tested. At 25°C, f = 1MHz. Outputs deselected.
7/20
M41T00
Table 5. DC CharacteristicsNote:1. Valid for Ambient Operating Temperature: TA = –40 to 85°C; VCC = 2.0 to 5.5V (except where noted). STMicroelectronics recommends the RAYOVAC BR1225 or BR1632 (or equivalent) as the battery supply. After switchover (VSO), VBAT(min) can be 2.0V for crystal with RS = 40KΩ. For rechargeable back-up, VBAT(max) may be considered VCC.
Table 6. Crystal Electrical CharacteristicsNote:1. These values are externally supplied. STMicroelectronics recommends the KDS DT-38: 1TA/1TC252E127, Tuning Fork Type (thru-
hole) or the DMX-26S: 1TJS125FH2A212, (SMD) quartz crystal for industrial temperature operations. KDS can be contacted at kou-
[email protected] or http://www.kdsj.co.jp for further information on this crystal type. Load capacitors are integrated within the M41T00. Circuit board layout considerations for the 32.768kHz crystal of minimum trace
lengths and isolation from RF generating signals should be taken into account.
M41T00
OPERATIONThe M41T00 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 8 bytes contained in the device
can then be accessed sequentially in the following
order: Seconds Register Minutes Register Century/Hours Register Day Register Date Register Month Register Years Register Control Register
The M41T00 clock continually monitors VCC for an
out of tolerance condition. Should VCC fall below
VSO, 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 VCC
falls below VSO, 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 bat-
tery to VCC at VSO and recognizes inputs.
2-Wire Bus CharacteristicsThis bus is intended for communication between
different ICs. It consists of two lines: one bi-direc-
tional for data signals (SDA) and one for clock sig-
nals (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:
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”.
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 relat-
ed 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 dur-
ing the High period of the acknowledge related
clock pulse. Of course, setup and hold times must
be taken into account. A master receiver must sig-
nal 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.
9/20
M41T00
Figure 6. Serial Bus Data Transfer Sequence
Figure 7. Acknowledgement Sequence
Figure 8. Bus Timing Requirements SequenceNote: P = STOP and S = START
M41T00
Table 7. AC CharacteristicsNote:1. Valid for Ambient Operating Temperature: TA = –40 to 85°C; VCC = 2.0 to 5.5V (except where noted). Transmitter must internally provide a hold time to bridge the undefined region (300ns max.) of the falling edge of SCL.
