M41T0 Serial real-time clock Features ■ Counters for seconds, minutes, hours, day, date, month, years, and century ■ 32 KHz crystal oscillator integrating load capacitance (12.5 pF) providing exceptional oscillator stability and high crystal series resistance operation ■ Oscillator stop detection monitors clock operation ■ Serial interface supports I2C bus (400 kHz protocol) ■ Low standby current 0.9 µA (typ at 3 V) ■ 2.0 to 5.
Contents M41T0 Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1 3 2-wire bus characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.1 Bus not busy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.
M41T0 List of tables List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
List of figures M41T0 List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. 4/23 Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 SOIC connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Block diagram . . . . . . . . . . . . . . . . . . .
M41T0 1 Description Description The M41T0 real-time clock is a low power serial real-time clock with a built-in 32.768 kHz oscillator (external crystal controlled). Eight registers are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. Addresses and data are transferred serially via a two-line bidirectional bus. The built-in address register is incremented automatically after each WRITE or READ data byte.
Description M41T0 Figure 3. Block diagram 1 Hz OSCI SECONDS OSCILLATOR 32.
M41T0 2 Operation Operation The M41T0 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 8 bytes contained in the device can then be accessed sequentially in the following order: 2.1 1. Seconds register 2. Minutes register 3. Century/hours register 4. Day register 5. Date register 6. Month register 7. Years register 8.
Operation 2.1.4 M41T0 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.
M41T0 Operation Figure 5. Acknowledgement sequence CLOCK PULSE FOR ACKNOWLEDGEMENT START SCLK FROM MASTER 1 DATA OUTPUT BY TRANSMITTER 2 8 MSB 9 LSB DATA OUTPUT BY RECEIVER AI00601 Figure 6. Bus timing requirements sequence SDA tBUF tHD:STA tHD:STA tR tF SCL tHIGH P S tLOW tSU:DAT tHD:DAT tSU:STA SR tSU:ST P AI00589 1.
Operation M41T0 Table 2. AC characteristics Parameter(1) Symbol Min Typ Max Unit 400 kHz fSCL SCL clock frequency tLOW Clock low period 1.
M41T0 2.3 Operation WRITE mode In this mode the master transmitter transmits to the M41T0 slave receiver. Bus protocol is shown in Figure 10 on page 12. Following the START condition 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.
Operation P NO ACK DATA n+X ACK BUS ACTIVITY: DATA n+1 ACK DATA n ACK S ACK SDA LINE R/W BUS ACTIVITY: MASTER STOP Alternate READ mode sequence START Figure 9. M41T0 SLAVE ADDRESS AI00895 STOP SLAVE ADDRESS 12/23 DATA n+X AI00591 Doc ID 9105 Rev 7 P ACK DATA n+1 ACK BUS ACTIVITY: DATA n ACK WORD ADDRESS (An) ACK S R/W SDA LINE ACK BUS ACTIVITY: MASTER START Figure 10.
M41T0 3 Clock operation Clock operation The M41T0 is driven by a quartz controlled oscillator with a nominal frequency of 32.768 kHz. The accuracy of the real-time clock depends on the frequency of the quartz crystal that is used as the time-base for the RTC. The M41T0 is tested to meet ± 35 ppm with nominal crystal. The eight-byte clock register (see Table 3 on page 14) is used to both set the clock and to read the date and time from the clock, in a binary coded decimal format.
Clock operation 3.3 M41T0 Initial power-on defaults Upon initial application of power to the device, the OUT bit and OF bit will be set to a '1,' while the ST bit will be set to '0.' All other register bits will initially power-on in a random state. Table 3.
M41T0 4 Maximum ratings Maximum ratings Stressing 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 indicated in the operating sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 4.
DC and AC parameters 5 M41T0 DC and AC parameters This section summarizes the operating and measurement 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 measurement conditions listed in the relevant tables. Designers should check that the operating conditions in their projects match the measurement conditions when using the quoted parameters. Table 5.
M41T0 DC and AC parameters Table 7. Sym DC characteristics Test condition(1) Parameter ILI Input leakage current ILO Output leakage current ICC1 Supply current Min Typ Max Unit 0V ≤ VIN ≤ VCC ±1 µA 0V ≤ VOUT ≤ VCC ±1 µA 3.0 V 35 55 µA 5.5 V 130 200 µA 3.0 V 0.9 1.2 µA 31 µA Frequency (SCL) = 400 kHz ICC2(2) Supply current (standby) All inputs = VCC – 0.2 V Frequency (SCL) = 0 Hz 5.5 V VIL Input low voltage –0.3 0.3 VCC V VIH Input high voltage 0.7 VCC VCC + 0.
Package mechanical information 6 M41T0 Package mechanical information In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Figure 12. SO8 – 8-lead plastic small outline, 150 mils body width, package mechanical drawing h x 45° A2 A c ccc b e 0.
M41T0 Package mechanical information Figure 13. Carrier tape for SO8 package (150 mils body width) P0 E P2 D T A0 F TOP COVER TAPE W B0 P1 CENTER LINES OF CAVITY K0 USER DIRECTION OF FEED AM03073v1 Table 10. Carrier tape dimensions for SO8 package (150 mils body width) Package W D SO8 12.00 ±0.30 1.50 +0.10/ –0.00 E P0 P2 F 1.75 4.00 2.00 5.50 ±0.10 ±0.10 ±0.10 ±0.05 A0 B0 K0 P1 T 6.50 ±0.10 5.30 ±0.10 2.20 ±0.10 8.00 ±0.10 0.30 ±0.
Package mechanical information M41T0 Figure 14. Reel schematic T 40mm min. Access hole At slot location B D C N A G measured Tape slot In core for Full radius Tape start 2.5mm min.width At hub AM04928v1 Table 11. Reel dimensions for 12 mm carrier tape - SO8 package (150 mils body width) A B (max) (min) 330 mm (13-inch) 1.5 mm Note: 20/23 C 13 mm ± 0.2 mm D N (min) (min) 20.2 mm 60 mm G 12.4 mm + 2/–0 mm T (max) 18.
M41T0 7 Part numbering Part numbering Table 12. Ordering information scheme Example: M41T 0 M 6 F Device type M41T Supply voltage and write protect voltage 0: VCC = 2.0 to 5.5 V Package M = SO8 (150 mils width) Temperature range 6 = –40 to 85 °C Shipping method E = ECOPACK® package, tubes F = ECOPACK® package , tape & reel For a list of additional options (e.g., speed, package) or for further information on any aspect of this device, please contact the ST sales office nearest to you.
Revision history 8 M41T0 Revision history Table 13. 22/23 Document revision history Date Revision Changes Feb-2003 1.0 First issue 18-Feb-2003 1.1 Add Pb-free information (Table 4, Table 12); update package information (Features, Figure 12; Table 12) 01-Apr-2003 1.2 Fix package outline and data (Features, Figure 12, Table 12) 10-Apr-2003 1.3 Revert to previous package (Features, Figure 12, Table 12) 30-Oct-2003 1.4 Remove footnote (Table 4) 30-Jun-2004 2.
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