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M41T94
512 Bit (64 bit x8) SERIAL RTC (SPI) SRAM
FEATURES SUMMARY s 2.7 TO 5.5V OPERATING VOLTAGE
s s
Figure 1. 16-pin SOIC Package
SERIAL PERIPHERAL INTERFACE (SPI) 2.5 TO 5.5V OSCILLATOR OPERATING VOLTAGE AUTOMATIC SWITCH-OVER and DESELECT CIRCUITRY CHOICE OF POWER-FAIL DESELECT VOLTAGES (VCC = 2.7 to 5.5V): - THS = VSS; 2.55V VPFD 2.70V - THS = VCC; 4.20V VPFD 4.50V Figure 2. 28-pin SOIC Package
16 1
s
SO16 (MQ)
s
s
COUNTERS FOR TENTHS/HUNDREDTHS OF SECONDS, SECONDS, MINUTES, HOURS, DAY, DATE, MONTH, YEAR, and CENTURY 44 BYTES OF GENERAL PURPOSE RAM PROGRAMMABLE ALARM and INTERRUPT FUNCTION (VALID EVEN DURING BATTERY BACK-UP MODE) WATCHDOG TIMER MICROPROCESSOR POWER-ON RESET BATTERY LOW FLAG LOW OPERATING CURRENT OF 2.0mA ULTRA-LOW BATTERY SUPPLY CURRENT OF 500nA (MAX) PACKAGING INCLUDES A 28-LEAD SOIC and SNAPHAT(R) TOP (to be ordered separately) or 16-LEAD SOIC 28-LEAD SOIC PACKAGE PROVIDES DIRECT CONNECTION FOR A SNAPHAT TOP WHICH CONTAINS THE BATTERY and CRYSTAL
SNAPHAT (SH) Battery & Crystal
s s
s s s s s
28 1
SOH28 (MH)
s
s
June 2003
Rev. 2.0
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M41T94
TABLE OF CONTENTS SUMMARY DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Figure 3. Logic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Table 1. Signal Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 4. 16-pin SOIC Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 5. 28-pin SOIC Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 6. Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 7. Hardware Hookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Table 2. Function Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 MAXIMUM RATING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 3. Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 DC AND AC PARAMETERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 4. DC and AC Measurement Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure 9. AC Testing Input/Output Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 5. Capacitance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 6. DC Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 7. Crystal Electrical Characteristics (Externally Supplied) . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 SPI Bus Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 10. Input Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 11. Output Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table 8. AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 READ and WRITE Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Figure 12. READ Mode Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Figure 13. WRITE Mode Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Data Retention Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Figure 14. Power Down/Up Mode AC Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Table 9. Power Down/Up AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 CLOCK OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 TIMEKEEPER(R) Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Table 10. TIMEKEEPER(R) Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Setting Alarm Clock Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Table 11. Alarm Repeat Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 15. Alarm Interrupt Reset Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 16. Back-up Mode Alarm Waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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M41T94
Square Wave Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Table 12. Square Wave Output Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Power-on Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Reset Inputs (RSTIN1 & RSTIN2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 17. RSTIN1 and RSTIN2 Timing Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Table 13. Reset AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Calibrating the Clock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Century Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Output Driver Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Battery Low Warning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 tREC Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Initial Power-on Defaults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Table 14. tREC Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Table 15. Default Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 18. Crystal Accuracy Across Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Figure 19. Calibration Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 PACKAGE MECHANICAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 PART NUMBERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Table 21. SNAPHAT Battery Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 REVISION HISTORY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
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M41T94
SUMMARY DESCRIPTION The M41T94 Serial TIMEKEEPER(R) SRAM is a low power, 512-bit static CMOS SRAM organized as 64 words by 8 bits. A built-in 32,768 Hz oscillator (external crystal controlled) and 8 bytes of the SRAM (see Table 10, page 17) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 12 bytes of RAM provide status/control of Alarm, Watchdog and Square Wave functions. Addresses and data are transferred serially via a serial SPI interface. The built-in address register is incremented automatically after each WRITE or READ data byte. The M41T94 has a built-in power sense circuit which detects power failures and automatically switches to the battery supply when a power failure occurs. The energy needed to sustain the SRAM and clock operations can be supplied by a small lithium button-cell supply when a power failure occurs. Functions available to the user include a non-volatile, time-of-day clock/calendar, Alarm interrupts, Watchdog Timer and programmable Square Wave output. Other features include a Power-On Reset as well as two additional debounced inputs (RSTIN1 and RSTIN2) which can also generate an output Reset (RST). The eight clock address locations contain the century, year, month, date, day, hour, minute, second and tenths/hundredths of a second in 24 hour BCD format. Corrections for 28, 29 (leap year - valid until year 2100), 30 and 31 day months are
made automatically. The ninth clock address location controls user access to the clock information and also stores the clock software calibration setting. The M41T94 is supplied in either a 16-lead plastic SOIC (requiring user supplied crystal and battery) or a 28-lead SOIC SNAPHAT(R) package (which integrates both crystal and battery in a single SNAPHAT top). The 28-pin, 330mil SOIC provides sockets with gold plated contacts at both ends for direct connection to a separate SNAPHAT housing containing the battery and crystal. The unique design allows the SNAPHAT battery/crystal package to be mounted on top of the SOIC package after the completion of the surface mount process. Insertion of the SNAPHAT housing after reflow prevents potential battery and crystal damage due to the high temperatures required for device surface-mounting. The SNAPHAT housing is also keyed to prevent reverse insertion. The SOIC and battery/crystal packages are shipped separately in plastic anti-static tubes or in Tape & Reel form. For the 28-lead SOIC, the battery/crystal package (e.g., SNAPHAT) part number is "M4TXX-BR12SH" (see Table 21, page 29). Caution: Do not place the SNAPHAT battery/crystal top in conductive foam, as this will drain the lithium button-cell battery.
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M41T94
Figure 3. Logic Diagram Table 1. Signal Names
E IRQ/FT/OUT Chip Enable Interrupt/Frequency Test/Out Output (Open Drain) Reset Output (Open Drain) Reset 1 Input Reset 2 Input Serial Clock Input Serial Data Input Serial Data Output Square Wave Output Threshold Select Pin Watchdog Input Oscillator Input Oscillator Output Battery Supply Voltage Supply Voltage Ground
VCC VBAT
(1)
RST
XI XO
(1) (1)
RSTIN1 RSTIN2
SCL SDI E RSTIN1 RSTIN2 WDI THS M41T94
RST IRQ/FT/OUT SQW SDO
SCL SDI SDO SQW THS WDI XI (1) XO (1)
VSS
AI03683
VBAT (1) VCC VSS
Note: 1. For SO16 package only.
Note: 1. For SO16 package only.
Figure 4. 16-pin SOIC Connections
Figure 5. 28-pin SOIC Connections
SQW NC NC NC NC NC NC WDI RSTIN1 RSTIN2 NC NC NC VSS 1 2 3 4 5 6 7 M41T94 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15
AI03685
XI XO RST WDI RSTIN1 RSTIN2 VBAT VSS
1 2 3 4 5 6 7 8
M41T94
16 15 14 13 12 11 10 9
AI03684
VCC E IRQ/FT/OUT THS SDI SQW SCL SDO
VCC E IRQ/FT/OUT NC NC THS NC NC SCL NC RST SDI SDO NC
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Figure 6. Block Diagram
E SDO SDI SCL SPI INTERFACE REAL TIME CLOCK CALENDAR 44 BYTES USER RAM RTC w/ALARM & CALIBRATION WATCHDOG SQUARE WAVE AF WDF
IRQ/FT/OUT
(1)
Crystal
32KHz OSCILLATOR
SQW
WDI VCC
VBAT VBL= 2.5V COMPARE BL
VSO = 2.5V
COMPARE
VPFD = 4.4V RSTIN1 RSTIN2
COMPARE
(2.65V if THS = VSS)
POR RST(1)
AI04785
Note: 1. Open drain output
Figure 7. Hardware Hookup
SPI Interface with (CPOL, CPHA)(1) = ('0','0') or ('1','1')
D Q C
Master (ST6, ST7, ST9, ST10, Others) CS3 CS2 CS1
C
Q
D
C
Q XXXXX
D
C
Q XXXXX
D
M41T94 E E
E
AI03686
Note: 1. CPOL (Clock Polarity) and CPHA (Clock Phase) are bits that may be set in the SPI Control Register of the MCU.
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Table 2. Function Table
Mode Disable Reset E H SCL Input Disabled SDI Input Disabled SDO High Z
WRITE
L
AI04630
Data Bit latch
High Z
READ
L
AI04631
X
Next data bit shift (1)
Note: 1. SDO remains at High Z until eight bits of data are ready to be shifted out during a READ.
Figure 8. Data and Clock Timing
CPOL CPHA
0
0
C
1
1
C
SDI
MSB
LSB
SDO
MSB
LSB
AI04632
Signal Description Serial Data Output (SDO). The output pin is used to transfer data serially out of the Memory. Data is shifted out on the falling edge of the serial clock. Serial Data Input (SDI). The input pin is used to transfer data serially into the device. Instructions, addresses, and the data to be written, are each received this way. Input is latched on the rising edge of the serial clock. Serial Clock (SCL). The serial clock provides the timing for the serial interface (as shown in Figure 10, page 12 and Figure 11, page 12). The W/R Bit, addresses, or data are latched, from the input pin, on the rising edge of the clock input. The output data on the SDO pin changes state after the falling edge of the clock input.
The M41T94 can be driven by a microcontroller with its SPI peripheral running in either of the two following modes: (CPOL, CPHA) = ('0', '0') or (CPOL, CPHA) = ('1', '1'). For these two modes, input data (SDI) is latched in by the low-to-high transition of clock SCL, and output data (SDO) is shifted out on the high-to-low transition of SCL (see Table 2, page 7 and Figure 8, page 7). Chip Enable (E). When E is high, the memory device is deselected, and the SDO output pin is held in its high impedance state. After power-on, a high-to-low transition on E is required prior to the start of any operation.
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M41T94
MAXIMUM RATING 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 Table 3. Absolute Maximum Ratings
Symbol TSTG VCC TSLD(1) VIO IO PD Parameter Storage Temperature (VCC Off, Oscillator Off) Supply Voltage Lead Solder Temperature for 10 seconds Input or Output Voltage Output Current Power Dissipation SNAPHAT SOIC Value -40 to 85 -55 to 125 -0.3 to 7 260 -0.3 to VCC+0.3 20 1 Unit C C V C V mA W
not implied. Exposure to Absolute Maximum Rating conditions for extended periods may affect device reliability. Refer also to the STMicroelectronics SURE Program and other relevant quality documents.
Note: 1. Reflow at peak temperature of 215C to 225C for < 60 seconds (total thermal budget not to exceed 180C for between 90 to 120 seconds).
CAUTION: Negative undershoots below -0.3V are not allowed on any pin while in the Battery Back-up mode. CAUTION: Do NOT wave solder SOIC to avoid damaging SNAPHAT sockets.
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M41T94
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 MeasureTable 4. DC and AC Measurement Conditions
Parameter VCC Supply Voltage Ambient Operating Temperature Load Capacitance (CL) Input Rise and Fall Times Input Pulse Voltages Input and Output Timing Ref. Voltages
Note: Output Hi-Z is defined as the point where data is no longer driven.
ment 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.
M41T94 2.7 to 5.5V -40 to 85C 100pF 50ns 0.2 to 0.8VCC 0.3 to 0.7VCC
Figure 9. AC Testing Input/Output Waveforms
0.8VCC
0.7VCC 0.3VCC
AI02568
0.2VCC
Table 5. Capacitance
Symbol CIN COUT tLP
(3)
Parameter(1,2) Input Capacitance Output Capacitance Low-pass filter input time constant (SDA and SCL)
Min
Max 7 10 50
Unit pF pF ns
Note: 1. Effective capacitance measured with power supply at 5V; sampled only, not 100% tested. 2. At 25C, f = 1MHz. 3. Outputs are deselected.
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Table 6. DC Characteristics
Symb. IBAT ICC1 ICC2 ILI(2) ILO(3) VIH VIL VBAT VOH VOL Parameter Battery Current OSC ON Battery Current OSC OFF Supply Current Supply Current (Standby) Input Leakage Current Output Leakage Current Input High Voltage Input Low Voltage Battery Voltage Output High Voltage(4) Output Low Voltage(4) Output Low Voltage (Open Drain)(5) Power Fail Deselect (THS = VCC) Power Fail Deselect (THS = VSS) VSO
Note: 1. 2. 3. 4. 5.
Test Condition(1) TA = 25C, VCC = 0V, VBAT = 3V f = 2 MHz SCL, SDI = VCC - 0.3V 0V VIN VCC 0V VOUT VCC
Min
Typ 400 50
Max 500
Unit nA nA
2 1.4 1 1 0.7VCC -0.3 2.5 VCC + 0.3 0.3VCC 3.5(6)
mA mA A A V V V V
IOH = -1.0mA IOL = 3.0mA IOL = 10mA
2.4 0.4
V 0.4 4.20 2.55 4.40 2.60 2.5 4.50 V 2.70 V Battery Back-up Switchover
VPFD
Valid for Ambient Operating Temperature: TA = -40 to 85C; VCC = 2.7 to 5.5V (except where noted). RSTIN1 and RSTIN2 internally pulled-up to VCC through 100K resistor. WDI internally pulled-down to VSS through 100K resistor. Outputs Deselected. For SQW pin (CMOS). For IRQ/FT/OUT, RST pins (Open Drain): if pulled-up to supply other than VCC, this supply must be equal to, or less than 3.0V when VCC = 0V (during battery back-up mode). 6. For rechargeable back-up, VBAT (max) may be considered VCC.
Table 7. Crystal Electrical Characteristics (Externally Supplied)
Symbol f0 RS CL Parameter(1,2) Resonant Frequency Series Resistance Load Capacitance 12.5 Typ 32.768 50 Min Max Unit kHz k pF
Note: 1. Load capacitors are integrated within the M41T94. Circuit board layout considerations for the 32.768 kHz crystal of minimum trace lengths and isolation from RF generating signals should be taken into account. These characteristics are externally supplied. 2. 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 kouhou@kdsj.co.jp or http://www.kdsj.co.jp for further information on this crystal type.
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M41T94
OPERATION The M41T94 clock operates as a slave device on the SPI serial bus. Each memory device is accessed by a simple serial interface that is SPI bus compatible. The bus signals are SCL, SDI and SDO (see Table 1, page 5 and Figure 7, page 6). The device is selected when the Chip Enable input (E) is held low. All instructions, addresses and data are shifted serially in and out of the chip. The most significant bit is presented first, with the data input (SDI) sampled on the first rising edge of the clock (SCL) after the Chip Enable (E) goes low. The 64 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. Century/Hours Register 5. Day Register 6. Date Register 7. Month Register 8. Year Register 9. Control Register 10. Watchdog Register 11 - 16.Alarm Registers 17 - 19.Reserved 20. Square Wave Register 21 - 64.User RAM The M41T94 clock continually monitors VCC for an out-of tolerance condition. Should VCC fall below VPFD, 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 a 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. As system power returns and VCC rises above VSO, the battery is disconnected, and the
power supply is switched to external VCC. Write protection continues until VCC reaches VPFD (min) plus tREC (min). For more information on Battery Storage Life refer to Application Note AN1012. SPI Bus Characteristics The Serial Peripheral interface (SPI) bus is intended for synchronous communication between different ICs. It consists of four signal lines: Serial Data Input (SDI), Serial Data Output (SDO), Serial Clock (SCL) and a Chip Enable (E). 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." The E input is used to initiate and terminate a data transfer. The SCL input is used to synchronize data transfer between the master (micro) and the slave (M41T94) devices. The SCL input, which is generated by the microcontroller, is active only during address and data transfer to any device on the SPI bus (see Figure 7, page 6). The M41T94 can be driven by a microcontroller with its SPI peripheral running in either of the two following modes: (CPOL, CPHA) = ('0', '0') or (CPOL, CPHA) = ('1', '1'). For these two modes, input data (SDI) is latched in by the low-to-high transition of clock SCL, and output data (SDO) is shifted out on the high-to-low transition of SCL (see Table 2, page 7 and Figure 8, page 7). There is one clock for each bit transferred. Address and data bits are transferred in groups of eight bits. Due to memory size the second most significant address bit is a Don't Care (address bit 6).
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M41T94
Figure 10. Input Timing Requirements
tEHEL E tELCH SCL tDVCH tCHDX SDI MSB IN tDLDH tDHDL tCLCH LSB IN tCHCL tCHEH tEHCH
SDO
HIGH IMPEDANCE
AI04633
Figure 11. Output Timing Requirements
E tCH SCL tCLQV tCLQX SDO
MSB OUT
tCL
tEHQZ
LSB OUT tQLQH tQHQL
SDI
ADDR. LSB IN AI04634
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M41T94
Table 8. AC Characteristics
Symbol fSCL tCH(2) tCHCL(3) tCHDX tCHEH tCL(2) tCLCH(3) tCLQV tCLQX tDHDL(3) tDLDH(3) tDVCH tEHCH tEHEL tEHQZ(3) tELCH tQHQL(3) tQLQH(3) Parameter(1) Serial Clock Input Frequency Clock High Clock Transition (Fall Time) Serial Clock Input High to Input Data Transition Serial Clock Input High to Chip Enable High Clock Low Clock Transition (Rise Time) Serial Clock Input Low to Output Valid Serial Clock Input Low to Output Data Transition Input Data Transition (Fall Time) Input Data Transition (Rise Time) Input Data to Serial Clock Input High Chip Enable High to Serial Clock Input High Chip Enable High to Chip Enable Low Chip Enable High to Output High-Z Chip Enable Low to Serial Clock Input High Output Data Transition (Fall Time) Output Data Transition (Rise Time) 200 100 100 40 200 200 250 0 1 1 50 200 200 1 150 Min DC 200 1 Max 2 Unit MHz ns s ns ns ns s ns ns s s ns ns ns ns ns ns ns
Note: 1. Valid for Ambient Operating Temperature: TA = -40 to 85C; VCC = 2.7 to 5.5V (except where noted). 2. tCH + tCL 1/fSCL 3. Value guaranteed by design, not 100% tested in production.
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M41T94
READ and WRITE Cycles Address and data are shifted MSB first into the Serial Data Input (SDI) and out of the Serial Data Output (SDO). Any data transfer considers the first bit to define whether a READ or WRITE will occur. This is followed by seven bits defining the address to be read or written. Data is transferred out of the SDO for a READ operation and into the SDI for a WRITE operation. The address is always the second through the eighth bit written after the Enable (E) pin goes low. If the first bit is a '1,' one or more WRITE cycles will occur. If the first bit is a '0,' one or more READ cycles will occur (see Figure 12 and Figure 13, page 15). Data transfers can occur one byte at a time or in multiple byte burst mode, during which the address pointer will be automatically incremented. For a single byte transfer, one byte is read or written and then E is driven high. For a multiple byte Figure 12. READ Mode Sequence
E 0 SCL W/R BIT 7 BIT ADDRESS 1 2 3 4 5 6 7 8 9 12 13 14 15 16 17 22
transfer all that is required is that E continue to remain low. Under this condition, the address pointer will continue to increment as stated previously. Incrementing will continue until the device is deselected by taking E high. The address will wrap to 00h after incrementing to 3Fh. The system-to-user transfer of clock data will be halted whenever the address being read is a clock address (00h to 07h). Although the clock continues to maintain the correct time, this will prevent updates of time and date during either a READ or WRITE of these address locations by the user. The update will resume either due to a deselect condition or when the pointer increments to an non-clock or RAM address (08h to 3Fh). Note: This is true both in READ and WRITE mode.
SDI
7 MSB
6
5
4
3
2
1
0 DATA OUT (BYTE 1) 7 MSB 6 5 4 3 2 1 0 7 MSB
AI04635
DATA OUT (BYTE 2) 6 5 4 3 2 1 0
SDO
HIGH IMPEDANCE
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M41T94
Figure 13. WRITE Mode Sequence
E 0 SCL 1 2 3 4 5 6 7 8 9 10 15
W/R BIT
7 BIT ADDR
DATA BYTE
SDI
7 MSB
6
5
4
3
2
1
0
7 MSB
6
5
4
3
2
1
0
7
SDO HIGH IMPEDANCE
AI04636
Data Retention Mode With valid VCC applied, the M41T94 can be accessed as described above with READ or WRITE cycles. Should the supply voltage decay, the M41T94 will automatically deselect, write protecting itself when VCC falls between VPFD (max) and VPFD (min) (see Figure 14, page 15). At this time, the Reset pin (RST) is driven active and will remain active until VCC returns to nominal levels. When VCC falls below the switch-over voltage (VSO ), power input is switched from the VCC pin to the SNAPHAT battery (or external battery for SO16) at this time, and the clock registers are Figure 14. Power Down/Up Mode AC Waveforms
VCC VPFD (max) VPFD (min) VSO tF tFB
maintained from the attached battery supply. All outputs become high impedance. On power up, when VCC returns to a nominal value, write protection continues for tREC by internally inhibiting E. The RST signal also remains active during this time (see Figure 14, page 15). Before the next active cycle, Chip Enable should be taken high for at least tEHEL, then low. For a further more detailed review of battery lifetime calculations, please see Application Note AN1012.
tR tRB tDR tREC
RECOGNIZED
INPUTS
RECOGNIZED
DON'T CARE
RST HIGH-Z OUTPUTS VALID
(PER CONTROL INPUT)
VALID
(PER CONTROL INPUT)
AI03687
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M41T94
Table 9. Power Down/Up AC Characteristics
Symbol tF(2) tFB(3) tR tRB tREC(5) tDR Parameter(1) VPFD (max) to VPFD (min) VCC Fall Time VPFD (min) to VSS VCC Fall Time VPFD (min) to VPFD (max) VCC Rise Time VSS to VPFD (min) VCC Rise Time Power up Deselect Time Expected Data Retention Time Min 300 10 10 1 40 10(4) 200 Typ Max Unit s s s s ms YEARS
Note: 1. Valid for Ambient Operating Temperature: TA = -40 to 85C; VCC = 2.7 to 5.5V (except where noted). 2. VPFD (max) to VPFD (min) fall time of less than tF may result in deselection/write protection not occurring until 200s after VCC passes VPFD (min). 3. VPFD (min) to VSS fall time of less than tFB may cause corruption of RAM data. 4. At 25C, VCC = 0V (when using SOH28 + M4T28-BR12SH SNAPHAT top). 5. Programmable (see Table 14, page 23)
CLOCK OPERATIONS The eight byte clock register (see Table 10, page 17) is used to both set the clock and to read the date and time from the clock, in a binary coded decimal format. Tenths/Hundredths of Seconds, Seconds, Minutes, and Hours are contained within the first four registers. Bits D6 and D7 of Clock Register 03h (Century/Hours Register) contain the CENTURY ENABLE Bit (CEB) and the CENTURY Bit (CB). Setting CEB to a '1' will cause CB to toggle, either from '0' to '1' or from '1' to '0' at the turn of the century (depending upon its initial state). If CEB is set to a '0,' CB will not toggle. Bits D0 through D2 of Register 04h contain the Day (day of week). Registers 05h, 06h, and 07h contain the Date (day of month), Month and Years. The ninth clock register is the Control Register (this is described in the Clock Calibration section). Bit D7 of Register 01h contains the STOP Bit (ST). Setting this bit to a '1' will cause the oscillator to stop. If the device is expected to spend a significant amount of time on the shelf, the oscillator may be stopped to reduce current drain. When reset to a '0' the oscillator restarts within one second. The eight Clock Registers may be read one byte at a time, or in a sequential block. The Control Register (Address location 08h) may be accessed independently. Provision has been made to assure that a clock update does not occur while any of the eight clock addresses are being read. If a clock address is being read, an update of the clock regis-
ters will be halted. This will prevent a transition of data during the READ. Note: When a power failure occurs, the Halt Update Bit (HT) will automatically be set to a '1.' This will prevent the clock from updating the clock registers, and will allow the user to read the exact time of the power-down event. Resetting the HT Bit to a '0' will allow the clock to update the clock registers with the current time. TIMEKEEPER (R) Registers The M41T94 offers 20 internal registers which contain Clock, Alarm, Watchdog, Flag, Square Wave and Control data (see Table 10, page 17). These registers are memory locations which contain external (user accessible) and internal copies of the data (usually referred to as BiPORTTM TIMEKEEPER cells). The external copies are independent of internal functions except that they are updated periodically by the simultaneous transfer of the incremented internal copy. The internal divider (or clock) chain will be reset upon the completion of a WRITE to any clock address. The system-to-user transfer of clock data will be halted whenever the clock addresses (00h to 07h) are being written. The update will resume either due to a deselect condition or when the pointer increments to a non-clock or RAM address. TIMEKEEPER and Alarm Registers store data in BCD. Control, Watchdog and Square Wave Registers store data in Binary format.
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M41T94
Table 10. TIMEKEEPER(R) Register Map
Addr D7 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 0Ah 0Bh 0Ch 0Dh 0Eh 0Fh 10h 11h 12h 13h OUT WDS AFE RPT4 RPT3 RPT2 RPT1 WDF 0 0 0 RS3 ST 0 CEB TR 0 0 CB 0 0 0 0 D6 D5 D4 D3 D2 D1 D0 Function/Range BCD Format Seconds Seconds Minutes Century/Hours Day Date Month Year Control RB1 RB0 Watchdog Al Month Al Date Al Hour Al Min Al Sec 0 0 0 0 0 Flags Reserved Reserved Reserved SQW 01-12 01-31 00-23 00-59 00-59 00-99 00-59 00-59 0-1/00-23 01-7 01-31 01-12 00-99
0.1 Seconds 10 Seconds 10 Minutes 10 Hours 0 10 Date 10M 0 0
0.01 Seconds Seconds Minutes Hours (24 Hour Format) Day of Week Date: Day of Month Month Year Calibration BMB2 Al 10M BMB1 BMB0
10 Years FT BMB4 SQWE RPT5 HT S BMB3 ABE
Alarm Month Alarm Date Alarm Hour Alarm Minutes Alarm Seconds 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
AI 10 Date AI 10 Hour
Alarm 10 Minutes Alarm 10 Seconds AF 0 0 0 RS2 0 0 0 0 RS1 BL 0 0 0 RS0
Keys: S = Sign Bit FT = Frequency Test Bit ST = Stop Bit 0 = Must be set to zero BL = Battery Low Flag (Read only) BMB0-BMB4 = Watchdog Multiplier Bits CEB = Century Enable Bit CB = Century Bit OUT = Output level AFE = Alarm Flag Enable Flag
RB0-RB1 = Watchdog Resolution Bits WDS = Watchdog Steering Bit ABE = Alarm in Battery Back-Up Mode Enable Bit RPT1-RPT5 = Alarm Repeat Mode Bits WDF = Watchdog flag (Read only) AF = Alarm flag (Read only) SQWE = Square Wave Enable RS0-RS3 = SQW Frequency HT = Halt Update Bit TR = tREC Bit
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M41T94
Setting Alarm Clock Registers Address locations 0Ah-0Eh contain the alarm settings. The alarm can be configured to go off at a prescribed time on a specific month, date, hour, minute, or second, or repeat every year, month, day, hour, minute, or second. It can also be programmed to go off while the M41T94 is in the battery back-up to serve as a system wake-up call. Bits RPT5-RPT1 put the alarm in the repeat mode of operation. Table 11, page 18 shows the possible configurations. Codes not listed in the table default to the once per second mode to quickly alert the user of an incorrect alarm setting. When the clock information matches the alarm clock settings based on the match criteria defined by RPT5-RPT1, the AF (Alarm Flag) is set. If AFE (Alarm Flag Enable) is also set, the alarm condition activates the IRQ/FT/OUT pin. Note: If the address pointer is allowed to increment to the Flag Register address, an alarm condition will not cause the Interrupt/Flag to occur until the address pointer is moved to a different adTable 11. Alarm Repeat Mode
RPT5 1 1 1 1 1 0 RPT4 1 1 1 1 0 0 RPT3 1 1 1 0 0 0 RPT2 1 1 0 0 0 0 RPT1 1 0 0 0 0 0 Alarm Setting Once per Second Once per Minute Once per Hour Once per Day Once per Month Once per Year
dress. It should also be noted that if the last address written is the "Alarm Seconds," the address pointer will increment to the Flag address, causing this situation to occur. To disable the alarm, write '0' to the Alarm Date Register and to RPT1-5. The IRQ/FT/OUT output is cleared by a READ to the Flags Register. This READ of the Flags Register will also reset the Alarm Flag (D6; Register 0Fh). See Figure 15, page 18. The IRQ/FT/OUT pin can also be activated in the battery back-up mode. The IRQ/FT/OUT will go low if an alarm occurs and both ABE (Alarm in Battery Back-up Mode Enable) and AFE are set. The ABE and AFE Bits are reset during power-up, therefore an alarm generated during power-up will only set AF. The user can read the Flag Register at system boot-up to determine if an alarm was generated while the M41T94 was in the deselect mode during power-up. Figure 16, page 19 illustrates the back-up mode alarm timing.
Figure 15. Alarm Interrupt Reset Waveforms
0Eh
0Fh
10h
ACTIVE FLAG
IRQ/FT/OUT
HIGH-Z
AI03664
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M41T94
Figure 16. Back-up Mode Alarm Waveforms
VCC VPFD
VSO tREC ABE, AFE Bits in Interrupt Register
AF bit in Flags Register
IRQ/FT/OUT HIGH-Z HIGH-Z
AI03920
Watchdog Timer The watchdog timer can be used to detect an outof-control microprocessor. The user programs the watchdog timer by setting the desired amount of time-out into the Watchdog Register, address 09h. Bits BMB4-BMB0 store a binary multiplier and the two lower order bits RB1-RB0 select the resolution, where 00 = 1/16 second, 01 = 1/4 second, 10 = 1 second, and 11 = 4 seconds. The amount of time-out is then determined to be the multiplication of the five-bit multiplier value with the resolution. (For example: writing 00001110 in the Watchdog Register = 3*1 or 3 seconds). Note: Accuracy of timer is within the selected resolution. If the processor does not reset the timer within the specified period, the M41T94 sets the WDF (Watchdog Flag) and generates a watchdog interrupt or a microprocessor reset. WDF is reset by reading the Flags Register (0Fh). The most significant bit of the Watchdog Register is the Watchdog Steering Bit (WDS). When set to a '0,' the watchdog will activate the IRQ/FT/OUT pin when timed-out. When WDS is set to a '1,' the watchdog will output a negative pulse on the RST pin for tREC. The Watchdog register and the AFE, ABE, SQWE, and FT Bits will reset to a '0' at the
end of a Watchdog time-out when the WDS Bit is set to a '1.' The watchdog timer can be reset by two methods: 1. a transition (high-to-low or low-to-high) can be applied to the Watchdog Input pin (WDI), or 2. the microprocessor can perform a WRITE of the Watchdog Register. The time-out period then starts over. The WDI pin should be tied to VSS if not used. In order to perform a software reset of the watchdog timer, the original time-out period can be written into the Watchdog Register, effectively restarting the count-down cycle. Should the watchdog timer time-out, and the WDS Bit is programmed to output an interrupt, a value of 00h needs to be written to the Watchdog Register in order to clear the IRQ/FT/OUT pin. This will also disable the watchdog function until it is again programmed correctly. A READ of the Flags Register will reset the Watchdog Flag (Bit D7; Register 0Fh). The watchdog function is automatically disabled upon power-up and the Watchdog Register is cleared. If the watchdog function is set to output to the IRQ/FT/OUT pin and the Frequency Test (FT) function is activated, the watchdog function prevails and the Frequency Test function is denied.
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M41T94
Square Wave Output The M41T94 offers the user a programmable square wave function which is output on the SQW pin. RS3-RS0 bits located in 13h establish the square wave output frequency. These frequencies are listed in Table 12. Once the selection of the Table 12. Square Wave Output Frequency
Square Wave Bits RS3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 RS2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 RS1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 RS0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Square Wave Frequency None 32.768 8.192 4.096 2.048 1.024 512 256 128 64 32 16 8 4 2 1 Units - kHz kHz kHz kHz kHz Hz Hz Hz Hz Hz Hz Hz Hz Hz Hz
SQW frequency has been completed, the SQW pin can be turned on and off under software control with the Square Wave Enable Bit (SQWE) located in Register 0Ah.
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M41T94
Power-on Reset The M41T94 continuously monitors VCC. When VCC falls to the power fail detect trip point, the RST pulls low (open drain) and remains low on powerup for tREC after VCC passes VPFD (max). The RST pin is an open drain output and an appropriate pull-up resistor should be chosen to control rise time. Reset Inputs (RSTIN1 & RSTIN2) The M41T94 provides two independent inputs which can generate an output reset. The duration and function of these resets is identical to a reset generated by a power cycle. Table 13, page 21 and Figure 17, page 21 illustrate the AC reset characteristics of this function. Pulses shorter than tRLRH1 and tRLRH2 will not generate a reset condition. RSTIN1 and RSTIN2 are each internally pulled up to VCC through a 100k resistor.
Figure 17. RSTIN1 and RSTIN2 Timing Waveforms
RSTIN1 tRLRH1 RSTIN2 tRLRH2 RST
(1)
tR1HRH
tR2HRH
AI03665
Table 13. Reset AC Characteristics
Symbol tRLRH1(2) tRLRH2(3) tR1HRH(4) tR2HRH(4)
Note: 1. 2. 3. 4.
Parameter(1) RSTIN1 Low to RSTIN1 High RSTIN2 Low to RSTIN2 High RSTIN1 High to RST High RSTIN2 High to RST High
Min 200 100 40 40
Max
Unit ns ms
200 200
ms ms
Valid for Ambient Operating Temperature: TA = -40 to 85C; VCC = 2.7 to 5.5V (except where noted). Pulse width less than 50ns will result in no RESET (for noise immunity). Pulse width less than 20ms will result in no RESET (for noise immunity). Programmable (see Table 14, page 23).
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M41T94
Calibrating the Clock The M41T94 is driven by a quartz-controlled oscillator with a nominal frequency of 32,768 Hz. Uncalibrated clock accuracy will not exceed 35 PPM (parts per million) oscillator frequency error at 25C, which equates to about 1.53 minutes per month. When the Calibration circuit is properly employed, accuracy improves to better than +1/-2 PPM at 25C. The oscillation rate of crystals changes with temperature (see Figure 18, page 24). Therefore, the M41T94 design employs periodic counter correction. The calibration circuit adds or subtracts counts from the oscillator divider circuit at the divide by 256 stage, as shown in Figure 19, page 24. The number of times pulses are blanked (subtracted, negative calibration) or split (added, positive calibration) depends upon the value loaded into the five Calibration Bits found in the Control Register. Adding counts speeds the clock up, subtracting counts slows the clock down. The Calibration Bits occupy the five lower order bits (D4-D0) in the Control Register (8h). These bits can be set to represent any value between 0 and 31 in binary form. Bit D5 is a Sign Bit; '1' indicates positive calibration, '0' indicates negative calibration. Calibration occurs within a 64 minute cycle. The first 62 minutes in the cycle may, once per minute, have one second either shortened by 128 or lengthened by 256 oscillator cycles. If a binary '1' is loaded into the register, only the first 2 minutes in the 64 minute cycle will be modified; if a binary 6 is loaded, the first 12 will be affected, and so on. Therefore, each calibration step has the effect of adding 512 or subtracting 256 oscillator cycles for every 125,829,120 actual oscillator cycles, that is +4.068 or -2.034 PPM of adjustment per calibration step in the calibration register. Assuming that the oscillator is running at exactly 32,768 Hz, each of the 31 increments in the Calibration byte would represent +10.7 or -5.35 seconds per month which corresponds to a total range of +5.5 or -2.75 minutes per month. Two methods are available for ascertaining how much calibration a given M41T94 may require. The first involves setting the clock, letting it run for a month and comparing it to a known accurate reference and recording deviation over a fixed period of time. Calibration values, including the number of
seconds lost or gained in a given period, can be found in Application Note AN934: TIMEKEEPER CALIBRATION. This allows the designer to give the end user the ability to calibrate the clock as the environment requires, even if the final product is packaged in a non-user serviceable enclosure. The designer could provide a simple utility that accesses the Calibration Byte. The second approach is better suited to a manufacturing environment, and involves the use of the IRQ/FT/OUT pin. The pin will toggle at 512 Hz, when the Stop Bit (ST, D7 of 1h) is '0,' the Frequency Test Bit (FT, D6 of 8h) is '1,' the Alarm Flag Enable Bit (AFE, D7 of Ah) is '0,' and the Watchdog Steering Bit (WDS, D7 of 9h) is '1' or the Watchdog Register (9h = 0) is reset. Any deviation from 512 Hz indicates the degree and direction of oscillator frequency shift at the test temperature. For example, a reading of 512.010124 Hz would indicate a +20 PPM oscillator frequency error, requiring a -10 (XX001010) to be loaded into the Calibration Byte for correction. Note: Setting or changing the Calibration Byte does not affect the Frequency Test output frequency. The IRQ/FT/OUT pin is an open drain output which requires a pull-up resistor for proper operation. A 500 to 10k resistor is recommended in order to control the rise time. The FT Bit is cleared on power-down. Century Bit Bits D7 and D6 of Clock Register 03h contain the CENTURY ENABLE Bit (CEB) and the CENTURY Bit (CB). Setting CEB to a '1' will cause CB to toggle, either from a '0' to '1' or from '1' to '0' at the turn of the century (depending upon its initial state). If CEB is set to a '0,' CB will not toggle. Output Driver Pin When the FT Bit, AFE Bit and Watchdog Register are not set, the IRQ/FT/OUT pin becomes an output driver that reflects the contents of D7 of the Control Register. In other words, when D7 (OUT Bit) and D6 (FT Bit) of address location 08h are a '0,' then the IRQ/FT/OUT pin will be driven low. Note: The IRQ/FT/OUT pin is an open drain which requires an external pull-up resistor.
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M41T94
Battery Low Warning The M41T94 automatically performs battery voltage monitoring upon power-up and at factory-programmed time intervals of approximately 24 hours. The Battery Low (BL) Bit, Bit D4 of Flags Register 0Fh, will be asserted if the battery voltage is found to be less than approximately 2.5V. The BL Bit will remain asserted until completion of battery replacement and subsequent battery low monitoring tests, either during the next power-up sequence or the next scheduled 24-hour interval. If a battery low is generated during a power-up sequence, this indicates that the battery is below approximately 2.5 volts and may not be able to maintain data integrity in the SRAM. Data should be considered suspect and verified as correct. A fresh battery should be installed. If a battery low indication is generated during the 24-hour interval check, this indicates that the battery is near end of life. However, data is not compromised due to the fact that a nominal VCC is supplied. In order to insure data integrity during subsequent periods of battery back-up mode, the battery should be replaced. The SNAPHAT top may be replaced while VCC is applied to the device.
Note: This will cause the clock to lose time during the interval the SNAPHAT battery/crystal top is disconnected. The M41T94 only monitors the battery when a nominal VCC is applied to the device. Thus applications which require extensive durations in the battery back-up mode should be powered-up periodically (at least once every few months) in order for this technique to be beneficial. Additionally, if a battery low is indicated, data integrity should be verified upon power-up via a checksum or other technique. tREC Bit Bit D7 of Clock Register 04h contains the tREC Bit (TR). tREC refers to the automatic continuation of the deselect time after VCC reaches VPFD. This allows for a voltage setting time before WRITEs may again be performed to the device after a powerdown condition. The tREC Bit will allow the user to set the length of this deselect time as defined by Table 14. Initial Power-on Defaults Upon initial application of power to the device, the following register bits are set to a '0' state: Watchdog Register, TR, FT, AFE, ABE, and SQWE. The following bits are set to a '1' state: ST, OUT, and HT (see Table 15).
Table 14. t REC Definitions
tREC Bit (TR) 0 0 1
Note: 1. Default Setting
STOP Bit (ST) Min 0 1 X 96 40 50
tREC Time Max 98 200(1) 2000
Units ms ms s
Table 15. Default Values
Condition Initial Power-up (Battery Attach for SNAPHAT)(2) Subsequent Power-up (with battery back-up)(3) TR 0 UC ST 1 UC HT 1 1 Out 1 UC FT 0 0 AFE 0 0 ABE 0 0 SQWE 0 0 WATCHDOG Register(1) 0 0
Note: 1. BMB0-BMB4, RB0, RB1. 2. State of other control bits undefined. 3. UC = Unchanged
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M41T94
Figure 18. Crystal Accuracy Across Temperature
Frequency (ppm) 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 F = -0.038 ppm (T - T )2 10% 0 F C2 T0 = 25 C
Temperature C
AI00999
Figure 19. Calibration Waveform
NORMAL
POSITIVE CALIBRATION
NEGATIVE CALIBRATION
AI00594B
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M41T94
PACKAGE MECHANICAL INFORMATION Figure 20. SO16 - 16-lead Plastic Small Outline Package Outline
A2 B e D
A C CP
N
E
1
H A1 L
SO-b
Note: Drawing is not to scale.
Table 16. SO16 - 16-lead Plastic Small Outline Package Mechanical Data
millimeters Symbol Typ. A A1 A2 B C D E e H L a N CP - - - - - - - - 1.27 - - - Min. - 0.10 - 0.35 0.19 9.80 3.80 - 5.80 0.40 0 16 - 0.10 - Max. 1.75 0.25 1.60 0.46 0.25 10.00 4.00 - 6.20 1.27 8 Typ. - - - - - - - 0.050 - - - Min. - 0.004 - 0.014 0.007 0.386 0.150 - 0.228 0.016 0 16 - 0.004 Max. 0.069 0.010 0.063 0.018 0.010 0.394 0.158 - 0.244 0.050 8 inches
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M41T94
Figure 21. SOH28 - 28-lead Plastic Small Outline, Battery SNAPHAT, Package Outline
A2 B e
A C eB CP
D
N
E
H A1 L
1 SOH-A
Note: Drawing is not to scale.
Table 17. SOH28 - 28-lead Plastic Small Outline, battery SNAPHAT, Package Mechanical Data
millimeters Symbol Typ A A1 A2 B C D E e eB H L N CP - - - - - - - - 1.27 - - - - Min - 0.05 2.34 0.36 0.15 17.71 8.23 - 3.20 11.51 0.41 0 28 - 0.10 - Max 3.05 0.36 2.69 0.51 0.32 18.49 8.89 - 3.61 12.70 1.27 8 Typ - - - - - - - 0.050 - - - - Min - 0.002 0.092 0.014 0.006 0.697 0.324 - 0.126 0.453 0.016 0 28 - 0.004 Max 0.120 0.014 0.106 0.020 0.012 0.728 0.350 - 0.142 0.500 0.050 8 inches
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M41T94
Figure 22. SH - 4-pin SNAPHAT Housing for 48mAh Battery & Crystal, Package Outline
A1
A2 A A3
eA D
B eB
L
E
SHTK-A
Note: Drawing is not to scale.
Table 18. SH - 4-pin SNAPHAT Housing for 48mAh Battery & Crystal, Package Mechanical Data
millimeters Symbol Typ A A1 A2 A3 B D E eA eB L - - - - - - - - - - Min - 6.73 6.48 - 0.46 21.21 14.22 15.55 3.20 2.03 Max 9.78 7.24 6.99 0.38 0.56 21.84 14.99 15.95 3.61 2.29 Typ - - - - - - - - - - Min - 0.265 0.255 - 0.018 0.835 0.556 0.612 0.126 0.080 Max 0.385 0.285 0.275 0.015 0.022 0.8560 0.590 0.628 0.142 0.090 inches
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M41T94
Figure 23. SH - 4-pin SNAPHAT Housing for 120mAh Battery & Crystal, Package Outline
A1
A2 A A3
eA D
B eB
L
E
SHTK-A
Note: Drawing is not to scale.
Table 19. SH - 4-pin SNAPHAT Housing for 120mAh Battery & Crystal, Package Mechanical Data
millimeters Symbol Typ A A1 A2 A3 B D E eA eB L - - - - - - - - - - Min - 8.00 7.24 - 0.46 21.21 17.27 15.55 3.20 2.03 Max 10.54 8.51 8.00 0.38 0.56 21.84 18.03 15.95 3.61 2.29 Typ - - - - - - - - - - Min - 0.315 0.285 - 0.018 0.835 0.680 0.612 0.126 0.080 Max 0.415 0.335 0.315 0.015 0.022 0.860 0.710 0.628 0.142 0.090 inches
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M41T94
PART NUMBERING Table 20. Ordering Information Scheme
Example: M41T 94 MH 6 TR
Device Type M41T
Supply Voltage and Write Protect Voltage 94 = VCC = 2.7 to 5.5V THS = VCC; 4.20V VPFD 4.50V THS = VSS; 2.55V VPFD 2.70V
Package MQ = SO16 MH (1) = SOH28
Temperature Range 6 = -40 to 85C
Shipping Method for SOIC blank = Tubes TR = Tape & Reel
Note: 1. The 28-pin SOIC package (SOH28) requires the battery/crystal package (SNAPHAT(R)) which is ordered separately under the part number "M4TXX-BR12SHX" in plastic tube or "M4TXX-BR12SHXTR" in Tape & Reel form. Caution: Do NOT place the SNAPHAT battery package "M4TXX-BR12SH" in conductive foam as it will drain the lithium button-cell battery.
For a list of available options (e.g., Speed, Package) or for further information on any aspect of this device, please contact the ST Sales Office nearest to you. Table 21. SNAPHAT Battery Table
Part Number M4T28-BR12SH M4T32-BR12SH Description Lithium Battery (48mAh) and Crystal SNAPHAT Lithium Battery (120mAh) and Crystal SNAPHAT Package SH SH
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REVISION HISTORY Table 22. Document Revision History
Date April 2002 25-Apr-02 03-Jul-02 06-Nov-02 26-Mar-03 28-Apr-03 Rev. # 1.0 1.1 1.2 1.3 1.4 2.0 First edition Adjust graphic (Figure 6); fix table text (Table 3, 20); adjust characteristics (Table 6. 7) Modify DC, Crystal Electrical Characteristics footnotes, Default Value table (Tables 6, 7, 15) Correct dimensions (Table 19) Update test condition (Table 9) New Si changes (Figure 6;Table 9, 13, 14, 15) Revision Details
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Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is registered trademark of STMicroelectronics All other names are the property of their respective owners. (c) 2003 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. www.st.com
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