Application Notes | Cross-Industry | General Purpose Products | Timekeeper | Timekeepers

VMEbus TIMEKEEPER® requirements

Application Note

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AN968 APPLICATION NOTE
VMEbus TIMEKEEPER Requirements

Surface-mount TIMEKEEPER devices, from STMicroelectronics, are designed explicitly for inclusion on CPU boards. A typical arrangement is shown in Figure 1. Figure 1. CPU module with a TIMEKEEPER Device

Local Microprocessor

Shared Memory

PCI Bus

Bridge

ISA Bus

Bus Interface TIMEKEEPER

VMEbus
AI02489

December 1998

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AN968 - APPLICATION NOTE
Each member of the TIMEKEEPER family provides support for the following functions:
s s s s s s

General timekeeping (i.e. seconds, hour, date, year,...) Time stamping (data collection correlated against time) Event sequencing during the manufacturing process Watchdog (to monitor for processes in the system that are out of control) RST: reset signal available for the CPU Non-volatile RAM (to store start-up parameters, ethernet address, etc.)

Most of the members of the TIMEKEEPER family (M48T02, M48T18, M48T559, M48T5X and M48T3X) are already being used by manufacturers of VME (Versa Module Eurocard) boards. However, the ones that are best suited for new `design-in' boards are the M48T59, M48T58 and the M48T559. These have the following features:
s

Automatic chip deselect and write protect when the power fails (as described in Application Note AN1012) BC D coded year, month, day, date, hours, minutes, and seconds (as described in Application Note AN923) Software calibration for increased clock accuracy (as described in Application Note AN934) 8K x 8 non-volatile static RAM (as described in Application Note AN1012) Microprocessor power-on reset (devices with 16-Byte register maps, only) (as described in Application Note AN924) Battery low warning software bit (devices with 16-Byte register maps, only) WDF interrupt function (devices with 16-Byte register maps, only) (as described in Application Note AN924) Periodic alarms (devices with 16-Byte register maps, only) Industry's first fully surface mountable TIMEKEEPER solution (as described in Application Note AN1019) Industry's smallest non-volatile TIMEKEEPER footprint (as shown in Application Note AN1019) Address/Address/Data Multiplex (M48T559 only) prevents the need for additional latch circuitry (as described in Application Note AN967).

s

s s s

s s

s s

s s

However, the significant feature is that each is available in ST's revolutionary SNAPHAT package: a standard SOIC that is surface mounted in the conventional way, and then is fitted with a SNAPHAT top, as shown in Figure 2, containing the battery and crystal. Figure 2. SOIC and SNAPHAT Package

AI02493

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AN968 - APPLICATION NOTE

If you have any questions or suggestions concerning the matters raised in this document, please send them to the following electronic mail addresses:

apps.nvram@ st.com ask.memory@ st.com

(for application support) (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 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. 1998 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 - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands - Singapore Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. http://www.st.com

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Document Number: 6255



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