memory products - Al Kossow's Bitsavers

MK48T02/12(B)-12115/20/25DESCRIPTIONThe MK48T02/12 combines a 2K x 8 full CMOSSRAM, a BYTEWIDE accessible real time clock, acrystal and a long life lithium carbon mono-fluoridebattery, all in a single plastic DIP package. TheMK48T02/12 is a non-volatile pin and functionequivalent to any JEDEC standard 2K x 8 SRAM,such as the 6116 or 5517. It also easily fits into manyEPROM AND EEPROM sockets, providing the nonvolatilityof the PROMs without any requirement forspecial write timing, or limitations on the numberof writes that can be performed.Access to the clock is as simple as conventionalBYTEWIDE RAM access because the RAM and theClock are combined on the same die. As Figure 2indicates, the TIMEKEEPER registers are locatedin the upper eight locations of the RAM. Theregisters contain, beginning at the top; year, month,date, day, hour, minutes, and seconds data in 24Hour BCD format. Corrections for 28, 29 (LeapYear), 30 and 31 day months are made automati-cally. The eighth location is a Control register. Theseregisters are not the actual clock counters; they areBiPORT read/write Static RAM memory locations.The MK48T02/12 includes a clock control circuitthat, once every second, dumps the counters intothe BiPORT RAM.Because the Clock Registers are constructed usingBiPORT memory cells, access to the rest of theRAM proceeds unhindered by updates to theTIMEKEEPER registers, even if the TIMEKEEPERregisters are being updated at the very momentanother location in the memory array is accessed.The MK48T02/12 also has its own Power-fail Detectcircuit. The circuit deselects the device wheneverVcc is out of range, providing a high degree of datasecurity in the midst of unpredictable system operationsbrought on by low Vce.BiPORT, BYTEWIDE, TIMEKEEPER and ZEROPOWERare trademarks of SGS-THOMSON Microelectronics, Inc ..FIGURE 2_ BLOCK DIAGRAMTOP HATrl-r------------,I I:.f III~ II132768 Hz!YSTAUI CRIIII L ITHIUMIELL II Cl 4IIIIIIIT:OSCILLATION ANDCLOCK CHAINVOLTAGE SENSEANDSWITCHINGCIRCUITRYI\~POWERPOKBOK• 8X8\ BIPORTj SRAM ARRAY IV-A/II\2040 X 8 A ISRAM /ARRAY \'jIIIIIL _-L __ -I ------- - _..J- L-Ao-A 10~DQo-DQ 7V-EViG2114300