Part # Application Note General Purpose Products M48T02 M48T08 M48T08Y M48T12 M48T18 M48T35AV M48T35Y M48T37V M48T37Y M48T58 M48T58Y M4 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: TIMEKEEPER rolling into the year 2000 (21st century, Y2K)

Part Details:

AN923 APPLICATION NOTE TIMEKEEPER Rolling into the Year 2000 (21st Century, Y2K) The members of the TIMEKEEPER family, from STMicroelectronics, are listed in Table 1. Each contains,in a single-package footprint, non-volatile RAM (NVRAM) and a real time clock (RTC), offering dedicatedtime-keeping and alarm functions. Table 1. Family of TIMEKEEPER Devices M41T56 Low cost RTC that is compatible with Serial I2C bus applications M48T86 RTC primarily utilized for its timekeeping functions with little additional memory M48T559 RTC with 64 Kbit memory that supports Address, Data Multiplexed I/O pins M48T02, M48T12, M48T08, M48T18, RTCs with 16 Kbit to 256 Kbit of additional asynchronous SRAM non-volatile M48T58, M48T59, M48T35, M48T37 memory M48T201 TIMEKEEPER SUPERVISOR CENTURY ROLLOVERThe date and time information is distributed over several internal registers, with two BCD digits in eachregister. Fabricated in ST s SRAM technology, the individual registers can be accessed by the user like aconventional bank of SRAM (read accesses to read the time, write accesses to set a new time). The year is divided into two fields: the Century field, and the Years field (each is 8 bits wide, holding twoBCD digits). TIMEKEEPER devices that were designed in 1997, and after, have a register for each ofthese fields; those that were designed before 1997, though, do not have the Century register. At the turn of the century, all TIMEKEEPERS will increment the Years register from 99 to 00 (from1001,1001 to 0000,0000). Those that have a Century register, will, at the same moment, increment it from19 to 20 (from 0001,1001 to 0010,0000). The Century register, where present, is positioned 14 address locations before the most significant byteaddress, using the device s 16-byte register map definition. For a 32K x 8 device, for example, the Centuryregister is at address location 7FF1h. For TIMEKEEPER devices that do not have a Century register, but which utilize the 16-byte register mapdefinition, it is recommended that the user sets up the same location (location 7FF1h for a 32K x 8 device,for example) for storing the Century information. This byte, of course, is not updated automatically by theclock, but has to be updated manually by the user s software. It is recommended that the user stores theBCD value 19 (0001,1001) in the location now, and on 1st January 2000, at 12:00:01 AM, updates it tothe BCD value 20 (0010,0000). TIMEKEEPER devices that do not have a Century register, and that do not utilize the 16-byte register mapdefinition, can still adopt the same methodology. Any address location that is convenient to the applicationcan be used for storing the Century information. Note: All TIMEKEEPERS automatically allow for 31, 30, 29 and 28 day months (correctly adjusting forleap-years until the year 2100). May 2000 1/2 AN923 - APPLICATION NOTE If you have any questions or suggestions concerning the matters raised in this document, please sendthem to the following electronic mail addresses: [email protected] (for application support) [email protected] (for general enquiries) Please remember to include your name, company, location, telephone number and fax number. Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequencesof 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 grantedby implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subjectto change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are notauthorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. © 2000 STMicroelectronics - All Rights Reserved The ST logo is a registered trademark of STMicroelectronics. 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. 2/2

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Application Note General Purpose Products M48T02 M48T08 M48T08Y M48T12 M48T18 M48T35AV M48T35Y M48T37V M48T37Y M48T58 M48T58Y M4.pdf Datasheet