M48T59 M48T59Y/M48T59V 64 Kbit (8Kb x8) TIMEKEEPER® SRAM PRELIMINARY DATA ■ INTEGRATED ULTRA LOW POWER SRAM, REAL TIME CLOCK, POWER-FAIL CONTROL CIRCUIT and BATTERY ■ FREQUENCY TEST OUTPUT for REAL TIME CLOCK SOFTWARE CALIBRATION ■ AUTOMATIC POWER-FAIL CHIP DESELECT and WRITE PROTECTION ■ WRITE PROTECT VOLTAGES (VPFD = Power-fail Deselect Voltage): – M48T59: 4.5V ≤ VPFD ≤ 4.75V – M48T59Y: 4.2V ≤ VPFD ≤ 4.5V – M48T59V: 2.7V ≤ VPFD ≤ 3.0V ■ SELF-CONTAINED BATTERY and CRYSTAL in the CAPHAT DIP PACKAGE ■ PACKAGING INCLUDES a 28-LEAD SOIC and SNAPHAT® TOP (to be Ordered Separately) ■ SOIC PACKAGE PROVIDES DIRECT CONNECTION for a SNAPHAT TOP which CONTAINS the BATTERY and CRYSTAL ■ MICROPROCESSOR POWER-ON RESET (Valid even during battery back-up mode) ■ PROGRAMMABLE ALARM OUTPUT ACTIVE in the BATTERY BACK-UP MODE ■ BATTERY LOW FLAG Table 1. Signal Names A0-A12 Address Inputs DQ0-DQ7 Data Inputs / Outputs IRQ/FT Interrupt / Frequency Test Output (Open Drain) RST Power Fail Reset Output (Open Drain) E Chip Enable G Output Enable W Write Enable VCC Supply Voltage VSS Ground SNAPHAT (SH) Battery/Crytstal 28 1 28 PCDIP28 (PC) Battery/Crystal CAPHAT 1 SOH28 (MH) Figure 1. Logic Diagram VCC 13 8 A0-A12 W E DQ0-DQ7 M48T59 M48T59Y M48T59V IRQ/FT RST G VSS AI01380E October 1999 This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice. 1/21 M48T59, M48T59Y, M48T59V Figure 2A. DIP Connections RST A12 A7 A6 A5 A4 A3 A2 A1 A0 DQ0 DQ1 DQ2 VSS Figure 2B. SOIC Connections 28 1 27 2 26 3 25 4 24 5 23 6 7 M48T59 22 8 M48T59Y 21 20 9 19 10 18 11 17 12 13 16 14 15 VCC W IRQ/FT A8 A9 A11 G A10 E DQ7 DQ6 DQ5 DQ4 DQ3 RST A12 A7 A6 A5 A4 A3 A2 A1 A0 DQ0 DQ1 DQ2 VSS 1 28 27 2 26 3 25 4 24 5 23 6 7 M48T59Y 22 8 M48T59V 21 20 9 19 10 18 11 17 12 16 13 15 14 AI01381D VCC W IRQ/FT A8 A9 A11 G A10 E DQ7 DQ6 DQ5 DQ4 DQ3 AI01382E Table 2. Absolute Maximum Ratings (1) Symbol TA TSTG TSLD (2) Parameter Value Ambient Operating Temperature Grade 1 0 to 70 Grade 6 –40 to 85 Storage Temperature (VCC Off, Oscillator Off) Lead Solder Temperature for 10 seconds Unit °C –40 to 85 °C 260 °C –0.3 to 7 V VIO Input or Output Voltages VCC Supply Voltage IO Output Current 20 mA PD Power Dissipation 1 W M48T59/M48T59Y –0.3 to 7 M48T59V –0.3 to 4.6 V Note: 1. Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to the absolute maximum rating conditions for extended periods of time may affect reliability. 2. Soldering temperature not to exceed 260°C for 10 seconds (total thermal budget not to exceed 150°C for longer than 30 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. Table 3. Operating Modes (1) Mode Deselect Write Read Read Deselect Deselect VCC E G W DQ7-DQ0 Power 4.75V to 5.5V or 4.5V to 5.5V or 3.0V to 3.6V VIH X X High Z Standby VIL X VIL DIN Active VIL VIL VIH DOUT Active VIL VIH VIH High Z Active X X X High Z CMOS Standby X X X High Z Battery Back-up Mode VSO to VPFD (min) ≤ VSO (2) Note: 1. X = VIH or VIL; VSO = Battery Back-up Switchover Voltage. 2. See Table 7 for details. 2/21 M48T59, M48T59Y, M48T59V Figure 3. Block Diagram IRQ/FT OSCILLATOR AND CLOCK CHAIN 16 x 8 BiPORT SRAM ARRAY 32,768 Hz CRYSTAL A0-A12 POWER DQ0-DQ7 8176 x 8 SRAM ARRAY LITHIUM CELL E VOLTAGE SENSE AND SWITCHING CIRCUITRY VCC W VPFD G RST VSS AI01383D DESCRIPTION The M48T59/59Y/59V TIMEKEEPER ® RAM is an 8Kb x8 non-volatile static RAM and real time clock. The monolithic chip is available in two special packages to provide a highly integrated battery backed-up memory and real time clock solution. The M48T59/59Y/59V is a non-volatile pin and function equivalent to any JEDEC standard 8Kb x8 SRAM. It also easily fits into many ROM, EPROM, and EEPROM sockets, providing the non-volatility of PROMs without any requirement for special write timing or limitations on the number of writes that can be performed. The 28 pin 600mil DIP CAPHAT™ houses the M48T59/59Y/59V silicon with a quartz crystal and a long life lithium button cell in a single package. 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 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 surfacemounting. The SNAPHAT housing is keyed to prevent reverse insertion. Table 4. AC Measurement Conditions ≤ 5ns Input Rise and Fall Times Input Pulse Voltages 0 to 3V Input and Output Timing Ref. Voltages 1.5V Note that Output Hi-Z is defined as the point where data is no longer driven. Figure 4. AC Testing Load Circuit 645Ω DEVICE UNDER TEST CL = 100pF CL includes JIG capacitance 1.75V AI02325 Note: Excluding open-drain output pins. 3/21 M48T59, M48T59Y, M48T59V Table 5. Capacitance (1, 2) (TA = 25 °C) Symbol CIN CIO (3) Parameter Test Condition Input Capacitance Input / Output Capacitance Min Max Unit VIN = 0V 10 pF VOUT = 0V 10 pF Note: 1. Effective capacitance measured with power supply at 5V. 2. Sampled only, not 100% tested. 3. Outputs deselected. Table 6. DC Characteristics (TA = 0 to 70 °C or –40 to 85 °C; VCC = 4.75V to 5.5V or 4.5V to 5.5V or 3.0V to 3.6V) M48T59/Y Symbol Parameter M48T59V Test Condition Unit Min ILI (1) Input Leakage Current ILO (1) Output Leakage Current Max Min Max 0V ≤ VIN ≤ VCC ±1 ±1 µA 0V ≤ VOUT ≤ VCC ±1 ±1 µA Outputs open 50 30 mA ICC Supply Current ICC1 Supply Current (Standby) TTL E = VIH 3 2 mA ICC2 Supply Current (Standby) CMOS E = VCC – 0.2V 3 1 mA VIL (2) Input Low Voltage –0.3 0.8 –0.3 0.8 V VIH Input High Voltage 2.2 VCC + 0.3 2 VCC + 0.3 V VOL VOH Output Low Voltage IOL = 2.1mA 0.4 0.4 V Output Low Voltage (IRQ/FT and RST) (3) IOL = 10mA 0.4 0.4 V Output High Voltage IOH = –1mA 2.4 2.4 V Note: 1. Outputs deselected. 2. Negative spikes of –1V allowed for up to 10ns once per cycle. 3. The IRQ/FT and RST pins are Open Drain. Table 7. Power Down/Up Trip Points DC Characteristics (1) (TA = 0 to 70 °C or –40 to 85 °C) Symbol VPFD VSO tDR Parameter Power-fail Deselect Voltage Min Typ Max Unit M48T59 4.5 4.6 4.75 V M48T59Y 4.2 4.35 4.5 V M48T59V 2.7 2.9 3.0 V M48T59/Y 3.0 V M48T59V VPFD –100mV V Battery Back-up Switchover Voltage Grade 1 7 YEARS Grade 6 10 (2) YEARS ExpectedDataRetentionTime(at25°C) Note: 1. All voltages referenced to VSS. 2. Using larger M4T32-BR12SH6 SNAPHAT top (recommended for Industrial Temperature Range - grade 6 device). 4/21 M48T59, M48T59Y, M48T59V Table 8. Power Down/Up AC Characteristics (TA = 0 to 70 °C or –40 to 85 °C) Symbol tPD Parameter Min E or W at VIH before Power Down tF (1) VPFD (max) to VPFD (min) VCC Fall Time tFB (2) VPFD (min) to VSS VCC Fall Time Max Unit 0 µs 300 µs M48T59/Y 10 µs M48T59V 150 µs tR VPFD (min) to VPFD (max) VCC Rise Time 10 µs tRB VSS to VPFD (min) VCC Rise Time 1 µs VPFD (max) to RST High 40 tREC (3) 200 ms Note: 1. VPFD (max) to VPFD (min) fall time of less than tF may result in deselection/write protection not occurring until 200µs after VCC passes V PFD (min). 2. VPFD (min) to VSS fall time of less than tFB may cause corruption of RAM data. 3. tREC (min) = 20ms for industrial temperature grade 6 device. Figure 5. Power Down/Up Mode AC Waveforms VCC VPFD (max) VPFD (min) VSO tF tR tFB tPD tRB tDR tREC RST INPUTS RECOGNIZED DON'T CARE RECOGNIZED HIGH-Z OUTPUTS VALID (PER CONTROL INPUT) VALID (PER CONTROL INPUT) AI03258 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 (i.e. SNAPHAT) part number is "M4T28-BR12SH" or “M4T32-BR12SH”. Caution: Do not place the SNAPHAT battery/crystal top in conductive foam, as this will drain the lithium button-cell battery. As Figure 3 shows, the static memory array and the quartz controlled clock oscillator of the M48T59/59Y/59V are integrated on one silicon chip. The two circuits are interconnected at the upper eight memory locations to provide user accessible BYTEWIDE™ clock information in the bytes with addresses 1FF8h-1FFFh. The clock locations contain the century, year, month, date, day, hour, minute, and second in 24 hour BCD format (except for the century). Corrections for 28, 29 (leap year), 30, and 31 day months are made automatically. Byte 1FF8h is the clock control register. This byte controls user access to the clock information and also stores the clock calibration setting. 5/21 M48T59, M48T59Y, M48T59V Table 9. Read Mode AC Characteristics (TA = 0 to 70 °C or –40 to 85 °C; VCC = 4.75V to 5.5V or 4.5V to 5.5V or 3.0V to 3.6V) M48T59/M48T59Y/M48T59V Symbol Parameter -70 Min tAVAV Read Cycle Time Unit Max 70 ns tAVQV (1) Address Valid to Output Valid 70 ns tELQV (1) Chip Enable Low to Output Valid 70 ns tGLQV (1) Output Enable Low to Output Valid 35 ns tELQX (2) Chip Enable Low to Output Transition 5 ns tGLQX (2) Output Enable Low to Output Transition 5 ns tEHQZ (2) Chip Enable High to Output Hi-Z 25 ns tGHQZ (2) Output Enable High to Output Hi-Z 25 ns tAXQX (1) Address Transition to Output Transition 10 ns Note: 1. CL = 100pF (see Fig 4). 2. CL = 5pF (see Fig 4). Figure 6. Read Mode AC Waveforms. tAVAV A0-A12 VALID tAVQV tAXQX tELQV tEHQZ E tELQX tGLQV tGHQZ G tGLQX DQ0-DQ7 VALID AI01385 Note: Write Enable (W) = High. 6/21 M48T59, M48T59Y, M48T59V Table 10. Write Mode AC Characteristics (TA = 0 to 70 °C or –40 to 85 °C; VCC = 4.75V to 5.5V or 4.5V to 5.5V or 3.0V to 3.6V) M48T59/M48T59Y/M48T59V Symbol Parameter -70 Min Unit Max tAVAV Write Cycle Time 70 ns tAVWL Address Valid to Write Enable Low 0 ns tAVEL Address Valid to Chip Enable Low 0 ns tWLWH Write Enable Pulse Width 50 ns tELEH Chip Enable Low to Chip Enable High 55 ns tWHAX Write Enable High to Address Transition 0 ns tEHAX Chip Enable High to Address Transition 0 ns tDVWH Input Valid to Write Enable High 30 ns tDVEH Input Valid to Chip Enable High 30 ns tWHDX Write Enable High to Input Transition 5 ns tEHDX Chip Enable High to Input Transition 5 ns tWLQZ (1, 2) Write Enable Low to Output Hi-Z 25 ns tAVWH Address Valid to Write Enable High 60 ns tAVE1H Address Valid to Chip Enable High 60 ns Write Enable High to Output Transition 5 ns tWHQX (1, 2) Note: 1. CL = 5pF (see Fig 4). 2. If E goes low simultaneously with W going low, the outputs remain in the high impedance state. The eight clock bytes are not the actual clock counters themselves; they are memory locations consisting of BiPORT™ read/write memory cells. The M48T59/59Y/59V includes a clock control circuit which updates the clock bytes with current information once per second. The information can be accessed by the user in the same manner as any other location in the static memory array. The M48T59/59Y/59V also has its own Power-fail Detect circuit. The control circuitry constantly monitors the single 5V supply for an out of tolerance condition. When V CC is out of tolerance, the circuit write protects the SRAM, providing a high degree of data security in the midst of unpredictable system operation brought on by low V CC. As VCC falls below approximately 3V, the control circuitry connects the battery which maintains data and clock operation until valid power returns. READ MODE The M48T59/59Y/59V is in the Read Mode whenever W (Write Enable) is high and E (Chip Enable) is low. The unique address specified by the 13 Address Inputs defines which one of the 8,192 bytes of data is to be accessed. Valid data will be available at the Data I/O pins within Address Access time (t AVQV) after the last address input signal is stable, providing that the E and G access times are also satisfied. If the E and G access times are not met, valid data will be available after the latter of the Chip Enable Access time (tELQV) or Output Enable Access time (tGLQV). The state of the eight three-state Data I/O signals is controlled by E and G. If the outputs are activated before t AVQV, the data lines will be driven to an indeterminate state until tAVQV. If the Address Inputs are changed while E and G remain active, output data will remain valid for Output Data Hold time (tAXQX) but will go indeterminate until the next Address Access. 7/21 M48T59, M48T59Y, M48T59V Figure 7. Write Enable Controlled, Write AC Waveform tAVAV VALID A0-A12 tAVWH tWHAX tAVEL E tWLWH tAVWL W tWHQX tWLQZ tWHDX DQ0-DQ7 DATA INPUT tDVWH AI01386 Figure 8. Chip Enable Controlled, Write AC Waveforms tAVAV A0-A12 VALID tAVEH tAVEL tELEH tEHAX E tAVWL W tEHDX DQ0-DQ7 DATA INPUT tDVEH AI01387B 8/21 M48T59, M48T59Y, M48T59V WRITE MODE The M48T59/59Y/59V is in the Write Mode whenever W and E are low. The start of a write is referenced from the latter occurring falling edge of W or E. A write is terminated by the earlier rising edge of W or E. The addresses must be held valid throughout the cycle. E or W must return high for a minimum of tEHAX from Chip Enable or tWHAX from Write Enable prior to the initiation of another read or write cycle. Data-in must be valid tDVWH prior to the end of write and remain valid for tWHDX afterward. G should be kept high during write cycles to avoid bus contention; although, if the output bus has been activated by a low on E and G a low on W will disable the outputs tWLQZ after W falls. DATA RETENTION MODE With valid V CC applied, the M48T59/59Y/59V operates as a conventional BYTEWIDE static RAM. Should the supply voltage decay, the RAM will automatically power-fail deselect, write protecting itself when V CC falls within the VPFD (max), VPFD (min) window. All outputs become high impedance, and all inputs are treated as "don’t care." Note: A power failure during a write cycle may corrupt data at the currently addressed location, but does not jeopardize the rest of the RAM’s content. At voltages below V PFD (min), the user can be assured the memory will be in a write protected state, provided the VCC fall time is not less than tF. The M48T59/59Y/59V may respond to transient noise spikes on VCC that reach into the deselect window Table 11. Register Map Data Address D7 1FFFh D6 D5 D4 D3 D2 10 Years 10 M D0 Year Year 00-99 Month Month 01-12 Date Date 01-31 Century/Day 00-01/01-07 Hours Hour 00-23 1FFEh 0 0 1FFDh 0 0 1FFCh 0 FT 1FFBh 0 0 1FFAh 0 10 Minutes Minutes Minutes 00-59 1FF9h ST 10 Seconds Seconds Seconds 00-59 1FF8h W R S 1FF7h WDS BMB4 BMB3 BMB2 BMB1 BMB0 RB1 RB0 Watchdog 1FF6h AFE Y ABE Y Y Y Y Y Interrupts 1FF5h RPT4 Y Al. 10 Date Alarm Date Alarm Date 01-31 1FF4h RPT3 Y Al. 10 Hours Alarm Hours Alarm Hours 00-23 1FF3h RPT2 Alarm 10 Minutes Alarm Minutes Alarm Minutes 00-59 1FF2h RPT1 Alarm 10 Seconds Alarm Seconds Alarm Seconds 00-59 1FF1h Y Y Y Y Y Y Y Y Unused 1FF0h WDF AF Z BL Z Z Z Z Flags Keys: 0 D1 Function/Range BCD Format 10 Date CB CEB 0 Day 10 Hours S = SIGN Bit FT = FREQUENCY TEST Bit R = READ Bit W = WRITE Bit ST = STOP Bit 0 = Must be set to zero Y = ’1’ or ’0’ Z = ’0’ and are Read only AF = Alarm Flag BL = Battery Low Calibration Control WDS = Watchdog Steering Bit BMB0-BMB4 = Watchdog Multiplier Bits RB0-RB1 = Watchdog Resolution Bits AFE = Alarm Flag Enable ABE = Alarm in Battery Back-up Mode Enable RPT1-RPT4 = Alarm Repeat Mode Bits WDF = Watchdog Flag CEB = Century Enable Bit CB = Century Bit 9/21 M48T59, M48T59Y, M48T59V during the time the device is sampling V CC. Therefore, decoupling of the power supply lines is recommended. When VCC drops below VSO, the control circuit switches power to the internal battery which preserves data and powers the clock. The internal button cell will maintain data in the M48T59/59Y/ 59V for an accumulated period of at least 7 years when VCC is less than V SO. As system power returns and V CC rises above VSO , the battery is disconnected, and the power supply is switched to external VCC. Deselect continues for tREC after VCC reaches VPFD (max). For more information on Battery Storage Life refer to the Application Note AN1012. POWER-ON RESET The M48T59/59Y/59V continuously monitors VCC. When V CC falls to the power fail detect trip point, the RST pulls low (open drain) and remains low on power-up for 40ms to 200ms after V CC passes VPFD. RST is valid for all VCC conditions. The RST pin is an open drain output and an appropriate resistor to VCC should be chosen to control rise time. PROGRAMMABLE INTERRUPTS The M48T59/59Y/59V provides two programmable interrupts; an alarm and a watchdog. When an interrupt condition occurs, the M48T59/59Y/59V sets the appropriate flag bit in the flag register 1FF0h. The interrupt enable bits in (AFE and ABE) in 1FF6h and the Watchdog Steering (WDS) bit in 1FF7h allow the interrupt to activate the IRQ/FT pin. The interrupt flags and the IRQ/FT output are cleared by a read to the flags register. An interrupt condition reset will not occur unless the addresses are stable at the flag location for at least 15ns while the divice is in the read mode as shown in Figure 11. The IRQ/FT pin is an open drain output and requires a pull-up resistor (10kΩ recommended) to VCC. The pin remains in the high impedance state unless an interrupt occurs or the frequency test mode is enabled. CLOCK OPERATIONS Reading the Clock Updates to the TIMEKEEPER registers should be halted before clock data is read to prevent reading data in transition. Because the BiPORT TIMEKEEPER cells in the RAM array are only data registers, and not the actual clock counters, updating the registers can be halted without disturbing the clock itself. Updating is halted when a ’1’ is written to the READ bit, D6 in the Control register (1FF8h). As long as a ’1’ remains in that position, updating is halted. After a halt is issued, the registers reflect the count; that is, the day, date, and the time that were current at the moment the halt command was issued. All of the TIMEKEEPER registers are updated simultaneously. A halt will not interrupt an update in progress. Updating is within a second after the bit is reset to a ’0’. Setting the Clock Bit D7 of the Control register (1FF8h) is the WRITE bit. Setting the WRITE bit to a ’1’, like the READ bit, halts updates to the TIMEKEEPER reg- Figure 9. Clock Calibration NORMAL POSITIVE CALIBRATION NEGATIVE CALIBRATION AI00594B 10/21 M48T59, M48T59Y, M48T59V isters. The user can then load them with the correct day, date, and time data in 24 hour BCD format (see Table 12). Resetting the WRITE bit to a ’0’ then transfers the values of all time registers (1FF9h-1FFFh) to the actual TIMEKEEPER counters and allows normal operation to resume. After the WRITE bit is reset, the next clock update will occur within approximately one second. See the Application Note AN923 "TIMEKEEPER rolling into the 21st century" for information on Century Rollover. Note: Upon power-up following a power failure, both the WRITE bit and the READ bit will be reset to ‘0’. Stopping and Starting the Oscillator The oscillator may be stopped at any time. If the device is going to spend a significant amount of time on the shelf, the oscillator can be turned off to minimize current drain on the battery. The STOP bit is the MSB of the seconds register. Setting it to a '1' stops the oscillator. The M48T59/59Y/59V in the DIP package, is shipped from STMicroelectronics with the STOP bit set to a '1'. When reset to a '0', the M48T59/59Y/59V oscillator starts within one second. Note: It is not necessary to set the WRITE bit when setting or resetting the FREQUENCY TEST bit (FT), the STOP bit (ST) or the CENTURY ENABLE bit (CEB). Calibrating the Clock The M48T59/59Y/59V is driven by a quartz controlled oscillator with a nominal frequency of 32,768Hz. The devices are tested not to exceed 35 ppm (parts per million) oscillator frequency error at 25°C, which equates to about ±1.53 minutes per month. With the calibration bits properly set, the accuracy of each M48T59/59Y/59V improves to better than +1/–2 ppm at 25°C. The oscillation rate of any crystal changes with temperature (see Figure 10). Most clock chips compensate for crystal frequency and temperature shift error with cumbersome trim capacitors. The M48T59/59Y/59V design, however, 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 9. The number of times pulses are blanked (subtracted, negative calibration) or split (added, positive calibration) depends upon the value loaded into the five bit Calibration byte found in the Control Register. Adding counts speeds the clock up, subtracting counts slows the clock down. The Calibration byte occupies the five lower order bits (D4-D0) in the Control register (1FF8h). 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 Figure 10. Crystal Accuracy Across Temperature Frequency (ppm) 20 0 –20 –40 –60 –80 –100 ∆F = -0.038 ppm (T - T )2 ± 10% 0 F C2 –120 T0 = 25 °C –140 –160 –40 –30 –20 –10 0 10 20 30 40 50 60 70 80 Temperature °C AI00999 11/21 M48T59, M48T59Y, M48T59V 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 in fact running at exactly 32,768Hz, 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 M48T59/59Y/59V may require. The first involves simply setting the clock, letting it run for a month and comparing it to a known accurate reference (like WWV broadcasts). While that may seem crude, it allows the designer to give the end user the ability to calibrate his clock as his environment may require, even after the final product is packaged in a non-user serviceable enclosure. All the designer has to do is 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 pin. The pin will toggle at 512Hz when the Stop bit (D7 of 1FF9h) is '0', the FT bit (D6 of 1FFCh) is '1', the AFE bit (D7 of 1FF6h) is '0', and the Watchdog Steering bit (D7 of 1FF7h) is '1' or the Watchdog Register is reset (1FF7h = 0). Any deviation from 512Hz indicates the degree and direction of oscillator frequency shift at the test temperature. For example, a reading of 512.01024 Hz would indicate a +20 ppm oscillator frequency error, requiring a –10 (WR001010) to be loaded into the Calibration Byte for correction. Note that setting or changing the Calibration Byte does not affect the Frequency test output frequency. The IRQ/FT pin is an open drain output which requires a pull-up resistor for proper operation. A 500-10kΩ resistor is recommended in order to control the rise time. The FT bit is cleared on power-down. For more information on calibration, see the Application Note AN934 "TIMEKEEPER Calibration". SETTING ALARM CLOCK Registers 1FF5h-1FF2h contain the alarm settings. The alarm can be configured to go off at a prescribed time on a specific day of the month or repeat every month, day, hour, minute, or second. It can also be programmed to go off while the M48T59 is in the battery back-up mode of operation to serve as a system wake-up call. RPT1-RPT4 put the alarm in the repeat mode of operation. Table 12 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. Table 12. Alarm Repeat Mode RPT4 RPT3 RPT2 RPT1 Alarm Activated 1 1 1 1 Once per Second 1 1 1 0 Once per Minute 1 1 0 0 Once per Hour 1 0 0 0 Once per Day 0 0 0 0 Once per Month Figure 11. Interrupt Reset Waveforms 15ns Min A0-A12 ADDRESS 1FF0h ACTIVE FLAG BIT IRQ/FT HIGH-Z AI01388B 12/21 M48T59, M48T59Y, M48T59V Note: User must transition address (or toggle chip enable) to see Flag bit change. When the clock information matches the alarm clock settings based on the match criteria defined by RPT1-RPT4, AF (Alarm Flag) is set. If AFE (Alarm Flag Enable) is also set, the alarm condition activates the IRQ/FT pin. To disable alarm, write ‘0’ to the Alarm Date register and RPT1-4. The alarm flag and the IRQ/FT output are cleared by a read to the Flags register. The IRQ/FT pin can also be activated in the battery back-up mode. The IRQ/FT 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 M48T59 was in the deselect mode during power-up. Figure 12 illustrates the back-up mode alarm timing. 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 eight bit Watchdog Register (Address 1FF7h). The five bits (BMB4-BMB0) store a binary multiplier and the two lower order bits (RB1RB0) 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 x 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 M48T59 sets the WDF (Watchdog Flag) and generates a watchdog interrupt or a microprocessor reset. WDF is reset by reading the Flags Register (Address 1FFOh). Figure 12. Back-up Mode Alarm Waveforms tREC VCC VPFD (max) VPFD (min) VSO ABE, AFE bit in Interrupt Register AF bit in Flags Register IRQ/FT HIGH-Z HIGH-Z AI03254B 13/21 M48T59, M48T59Y, M48T59V 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 voltage is below 2.5V (approximately), which may be insufficient to maintain data integrity. 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 has not been 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, it is recommended that the battery be replaced. The SNAPHAT top may be replaced while VCC is applied to the device. Note: Battery monitoring is a useful technique only when performed periodically. The M48T59/59Y/ 59V 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. The most significant bit of the Watchdog Register is the Watchdog Steering Bit. When set to a ’0’, the watchdog will activate the IRQ/FT pin when timedout. When WDS is set to a ’1’, the watchdog will output a negative pulse on the RST pin for a duration of 40ms to 200ms. The Watchdog register and the FT bit 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 resets when the microprocessor performs a re-write of the Watchdog Register. The time-out period then starts over. The watchdog timer is disabled by writing a value of 00000000 to the eight bits in the Watchdog Register. The watchdog function is automatically disabled upon power-down and the Watchdog Register is cleared. If the watchdog function is set to output to the IRQ/FT pin and the frequency test function is activated, the watchdog or alarm function prevails and the frequency test function is denied. BATTERY LOW FLAG The M48T59/59Y/59V automatically performs periodic battery voltage monitoring upon power-up and at factory-programmed time intervals of 24 hours (at day rollover) as long as the device is powered and the oscillator is running. The Battery Low flag (BL), Bit D4 of the flags Register 1FF0h, will be asserted high if the internal or SNAPHAT battery is found to be less than approximately 2.5V. The BL flag will remain active until completion of battery replacement and subsequent battery low monitoring tests, either during the next POWER-ON DEFAULTS Upon application of power to the device, the following register bits are set to a ’0’ state: WDS; BMB0-BMB4; RB0-RB1; AFE; ABE; W; R; FT. (See Table 13). Table 13. Default Values W R FT AFE ABE WATCHDOG Register (1) Initial Power-up (Battery Attach for SNAPHAT) (2) 0 0 0 0 0 0 Subsequent Power-up / RESET (3) 0 0 0 0 0 0 Power-down (4) 0 0 0 1 1 0 Condition Note: 1. 2. 3. 4. 14/21 WDS, BMB0-BMB4, RBO, RB1. State of other control bits undefined. State of other control bits remains unchanged. Assuming these bits set to ’1’ prior to power-down. M48T59, M48T59Y, M48T59V POWER SUPPLY DECOUPLING and UNDERSHOOT PROTECTION ICC transients, including those produced by output switching, can produce voltage fluctuations, resulting in spikes on the VCC bus. These transients can be reduced if capacitors are used to store energy, which stabilizes the V CC bus. The energy stored in the bypass capacitors will be released as low going spikes are generated or energy will be absorbed when overshoots occur. A ceramic bypass capacitor value of 0.1µF (as shown in Figure 13) is recommended in order to provide the needed filtering. In addition to transients that are caused by normal SRAM operation, power cycling can generate negative voltage spikes on V CC that drive it to values below V SS by as much as one Volt. These negative spikes can cause data corruption in the SRAM while in battery backup mode. To protect from these voltage spikes, it is recommended to connect a schottky diode from V CC to VSS (cathode connected to VCC, anode to VSS). Schottky diode 1N5817 is recommended for through hole and MBRS120T3 is recommended for surface mount Figure 13. Supply Voltage Protection VCC VCC 0.1µF DEVICE VSS AI02169 15/21 M48T59, M48T59Y, M48T59V Table 14. Ordering Information Scheme Example: M48T59Y -70 MH 1 TR Device Type M48T Supply Voltage and Write Protect Voltage 59 (1) = VCC = 4.75V to 5.5V; VPFD = 4.5V to 5.5V 59Y = VCC = 4.5V to 5.5V; VPFD = 4.2V to 4.5V 59V = VCC = 3.0V to 3.6V; VPFD = 2.7V to 3.0V Speed -70 = 70ns Package PC = PCDIP28 MH (2) = SOH28 Temperature Range 1 = 0 to 70 °C 6 (3) = –40 to 85 °C Shipping Method for SOIC blank = Tubes TR = Tape & Reel Note: 1. The M48T59 part is offered with the PCDIP28 (i.e. CAPHAT) package only. 2. The SOIC package (SOH28) requires the battery/crystal package (SNAPHAT) which is ordered separately under the part number "M4TXX-BR12SH1" in plastic tube or "M4TXX-BR12SH1TR" in Tape & Reel form. 3. Available in SOIC package only. Caution: Do not place the SNAPHAT battery/crystal package "M4TXX-BR12SH1" in conductive foam since will drain the lithium buttoncell battery. For a list of available options (Speed, Package, etc...) or for further information on any aspect of this device, please contact the ST Sales Office nearest to you. 16/21 M48T59, M48T59Y, M48T59V Table 15. PCDIP28 - 28 pin Plastic DIP, battery CAPHAT, Package Mechanical Data mm inches Symb Typ Min Max A 8.89 A1 Typ Min Max 9.65 0.350 0.380 0.38 0.76 0.015 0.030 A2 8.38 8.89 0.330 0.350 B 0.38 0.53 0.015 0.021 B1 1.14 1.78 0.045 0.070 C 0.20 0.31 0.008 0.012 D 39.37 39.88 1.550 1.570 E 17.83 18.34 0.702 0.722 e1 2.29 2.79 0.090 0.110 e3 29.72 36.32 1.170 1.430 eA 15.24 16.00 0.600 0.630 L 3.05 3.81 0.120 0.150 N 28 28 Figure 14. PCDIP28 - 28 pin Plastic DIP, battery CAPHAT, Package Outline A2 A1 B1 B e1 A L C eA e3 D N E 1 PCDIP Drawing is not to scale. 17/21 M48T59, M48T59Y, M48T59V Table 16. SOH28 - 28 lead Plastic Small Outline, battery SNAPHAT, Package Mechanical Data mm inches Symb Typ Min Max A Typ Min 3.05 0.120 A1 0.05 0.36 0.002 0.014 A2 2.34 2.69 0.092 0.106 B 0.36 0.51 0.014 0.020 C 0.15 0.32 0.006 0.012 D 17.71 18.49 0.697 0.728 E 8.23 8.89 0.324 0.350 – – – – eB 3.20 3.61 0.126 0.142 H 11.51 12.70 0.453 0.500 L 0.41 1.27 0.016 0.050 α 0° 8° 0° 8° N 28 e 1.27 0.050 28 CP 0.10 0.004 Figure 15. SOH28 - 28 lead Plastic Small Outline, battery SNAPHAT, Package Outline A2 A C B eB e CP D N E H A1 1 SOH-A Drawing is not to scale. 18/21 Max α L M48T59, M48T59Y, M48T59V Table 17. M4T28-BR12SH SNAPHAT Housing for 48 mAh Battery & Crystal, Package Mechanical Data mm inches Symb Typ Min A Max Typ Min Max 9.78 0.385 A1 6.73 7.24 0.265 0.285 A2 6.48 6.99 0.255 0.275 A3 0.38 0.015 B 0.46 0.56 0.018 0.022 D 21.21 21.84 0.835 0.860 E 14.22 14.99 0.560 0.590 eA 15.55 15.95 0.612 0.628 eB 3.20 3.61 0.126 0.142 L 2.03 2.29 0.080 0.090 Figure 16. M4T28-BR12SH SNAPHAT Housing for 48 mAh Battery & Crystal, Package Outline A1 eA A2 A A3 B L eB D E SHTK-A Drawing is not to scale. 19/21 M48T59, M48T59Y, M48T59V Table 18. M4T32-BR12SH SNAPHAT Housing for 120mAh Battery & Crystal, Package Mechanical Data mm inches Symb Typ Min A Max Typ Min Max 10.54 0.415 A1 8.00 8.51 0.315 0.335 A2 7.24 8.00 0.285 0.315 A3 0.38 0.015 B 0.46 0.56 0.018 0.022 D 21.21 21.84 0.835 0.860 E 17.27 18.03 0.680 0.710 eA 15.55 15.95 0.612 0.628 eB 3.20 3.61 0.126 0.142 L 2.03 2.29 0.080 0.090 Figure 17. M4T32-BR12SH SNAPHAT Housing for 120mAh Battery & Crystal, Package Outline A1 eA A2 A A3 B L eB D E SHTK-A Drawing is not to scale. 20/21 M48T59, M48T59Y, M48T59V . 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 1999 STMicroelectronics - All Rights Reserved All other names are the property of their respective owners. STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. http://www.st.com 21/21