memory products - Al Kossow's Bitsavers

MK4202(Q)-20The net effect Is that the Address-to-Compare accesstime demonstrated by the MK4202 is all of thedelay the user must consider. The alternative approach,using narrow TAG RAMs with open collectoroutputs or narrow TAGRAMs with 2-state outputsand a 10ns programmable logic device, requiresthat the narrow TAG RAMs demonstrate a 10nsAddress-to-Compare access time to yield the sameperformance in a user's system that the MK4202provides.POWER DISTRIBUTIONThe MK4202, being a 20 output device, obviouslyrequires the use of good power bussing techniques.MK4202 has been designed in such a way as to allowthe user to minimize the effects of switchingtransients on overall circuit operation. Of particuFIGURE 4. APPLICATION BLOCK SCHEMATICI P = 0001INDEX11P = 0000A. A,.lar interest is the separate bussing of the Vcc andVss lines to the output drivers. The advantageprovided by these separate power pins .. designatedVcca and VSSQ, is that voltage sags and groundbumps seen on these pins are not reflected into theother portions of the chip, particularly the inputstructures. As a result, switching noise in the supplyhas much less effect on input levels, providingthe user with more noise margin than would otherwisebe available.Of course Vss and Vssa must always be at thesame DC potential. Vcc and Vcca must match aswell. Differences between them due to AC effectsare expected, but must be minimized through theuse of adequate bussing and bypassing. All specificationsand testing are done with V ss = V ssa ±10mV RMS, Vcc = Vcca ± 10mV RMS with instantaneouspeak differences not exceeding 50mV.32 BIT .p1INDEX Eo E,TAG19DO, DO,.VALIDCDO.SELECTSWRITEWREAD G C.BUS ERR M.HALT M, C,c·nc'nVeeQ~>BERRHALTH.H,CG.>~?VeeCG,5118369