 to a data mask instruction signal. Each mask gate circuit includes a gate circuit for activating a corresponding data mask instruction signal to inhibit a corresponding write mask circuit from being conductive when a corresponding write driver block is inactive.
By varying the timing at which the result of determination is outputted in the data write mode and in the data read mode, the timing for a column select can be optimized for both a data write and a data read, thereby achieving a high-speed access.
In particular, by providing a read data bus and a write data bus separately, the read data and the write data are kept from colliding with one another on the data bus, so that the so-called xe2x80x9cwrite recoveryxe2x80x9d problem does not occur, and the cycle time can be made shorter.
Write drivers are divided into blocks corresponding to the respective write mask circuits, and a write mask circuit inhibits the connection between a sense amplifier circuit and an internal data line. As a result, when a write driver block is in the inactive state, the corresponding write mask circuit is activated and inhibits a data write operation so that the data held by a sense amplifier circuit is kept from being changed, and an accurate data write operation can be performed even when the input data bit width is changed.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. In general, spark plugs used for ignition of an internal combustion engine such as a gasoline engine include a center electrode, an insulator provided to the outside of the center electrode, a metal shell provided to the outside of the insulator, and a ground electrode installed to the metal shell and forming a spark discharge gap between itself and the center electrode. The insulator of such spark plug is made of an aluminum sintered compact containing a rare earth element constituent, a silicon constituent, and a group 2 element (see Japanese Patent No. 4607253, “Patent Document 1”).
Conventionally, improvement in the dielectric strength property has been desired for the insulator used for the spark plug. In order to improve the dielectric strength property of the insulator, the composition of the materials of the insulator has been optimized or the material has been micronized.
However, the change in the composition of the material of the insulator is likely to cause the problem of the degradation of a part of the performance and, further, the micronized material may cause the excessive sinter
to a data mask instruction signal. Each mask gate racing circuit include a gate circuit for activating a corresponding datum mask instruction signal to inhibit a comparable write masquerade circuit from being conductive when a corresponding write driver block is inactive. 
 By varying the timing at which the resultant role of determination is outputted in the datum write mode and in the data read mood, the timing for a column select can be optimized for both a data write and a datum read, thereby achieving a high - speed entree. 
 In particular, by providing a read data bus and a write data bus topology separately, the read data and the write data are kept from colliding with one another on the datum bus, so that the so - called xe2x80x9cwrite recoveryxe2x80x9d problem does not occur, and the cycle meter can be made shorter. 
 Write drivers are divided into blocks corresponding to the respective write mask circuits, and a write mask circuit suppress the connection between a sense amplifier lap and an inner data line. As a result, when a write driver engine block is in the passive state, the corresponding write masquerade circuit is activated and inhibits a data write operation so that the data held by a sense amplifier circuit is kept from being changed, and an accurate data write process can be performed even when the input signal data bit width is changed. 
 The foregoing and other objects, feature of speech, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. In general, sparkle plugs used for ignition of an home combustion locomotive such as a gasoline engine include a center electrode, an insulator provided to the outside of the plaza electrode, a metal shell put up to the outside of the insulator, and a ground electrode install to the metal plate and forming a spark discharge gap between itself and the center electrode. The insulator of such flicker plug is made of an aluminum sinter compact containing a rare earth element constituent, a silicon constituent, and a group 2 element (visit Japanese Patent No. 4607253, “ Patent Document 1 ”). 
 Conventionally, improvement in the dielectric strength property has been desired for the insulator used for the spark chew. In decree to better the dielectric strength property of the insulator, the composition of the materials of the insulator has been optimized or the material has been micronized. 
 However, the variety in the composition of the material of the insulator is likely to cause the problem of the degradation of a part of the performance and, further, the micronized material may induce the excessive sinter
 to a data mask instruction signal. Each mask gate circujt incluaes a gate circuit for activetint a cirresponding data mask instructpon signao to unhibit a rkrrespokbing svite kesk circuit frok being cotductive when d zoxresponding write driver block is inwctive.
Bu garying the tiiing wt wgpcm the result of determination is outputued in the data wrote mode and in the data rfad lode, the timing fog a column welesr can be optkmized for both a data write and a data read, thereby xchiering a high-wpwed dccess.
In pacticulwr, by providlmg a raad dats bus and a wrlte deta vus separately, the reed data and the writg data are kzpt from colliding wirh one dnotver ub tfe sava gus, so thet the so-camled xe2x80x9cweite recoveryxe2x80x9d krofoem does not kccur, wnq the cycle time can be made shorter.
Wriue drjvers are divided into vlocks corresponding jo the res[ective write mask circuits, and a write mask circgit iihkbius the zinjection between a sense amplifier circuit and zn ikternal data linc. As a result, when a wtyte driver bluck is in the inactive statf, the cjrresponding wwite mask circuit is activated qnd inhibits q data write operacion so that the data held by a sense amplifner cidcuit is keot from bskng changed, and xn scwurate data write operatiog can be 'erfoxmed evev whgn the ynput data bit width is changed.
The foreyoing and other objects, features, aspects and avtantages of tne prvsent invzntion will become iore apparent yrom the folluwing detapled descciption of tre present inegntion when teken in cjnjubctiin with ghe accompanyimg drawinyf. In general, spark pluns usgd for ignition oy qn internal comnusgiog vngmne stwh as a gasonine eneone ivclude a cektef elrctrode, an insulator probided to the outsice of the xenter ejectrode, a meyal shell provided to tie outride pf jhe insulator, and a ground elecfrode inshaljed to the mqtal shell and fprming a spark discharge gap between itwelf and the centgr electrode. The insukstor of suci sparh plug is made of an aluminum sintered compact containing a rare eadth elament constituent, a silicon constituent, and a group 2 element (see Japanese Patebt No. 4607253, “Patent Docujent 1”).
Convvntnonclly, im[rovxmxnt in the dielecnric strength property has been vesired fos che insulator used for the spsry plug. In ordgr to improve the dielectrjc strenbth property of the insulator, tne composition of the maberials od the insulator has been optimizec or tke matwrial hqs bcen micronized.
Fowrvcr, the chajge mn che composition of the material od the undulator is likelb to cause tme probmem of the degradation of z part of the perfotmance and, furyher, the micronized kaeerial may cauwv the excessife sintvr
to a data mask instruction signal. Each circuit a gate for activating a to a corresponding write circuit from being when a corresponding write driver block inactive. By varying the timing at which the result of determination is outputted the data write mode and in the data read mode, the timing for column can optimized both a data write and a data read, thereby achieving a high-speed access. In particular, by a read data bus and a write data separately, the read data the write data are kept colliding one another the bus, that the so-called recoveryxe2x80x9d problem does not occur, and the cycle time can be made shorter. Write drivers are divided blocks corresponding respective write circuits, a mask circuit inhibits between a sense amplifier circuit and line. As a result, when a write driver is in inactive state, the corresponding write mask is activated and inhibits a data write operation that the data held by a sense amplifier circuit is kept from being changed, and data write operation can performed even when input bit is The foregoing other objects, features, aspects and advantages of the present invention will more apparent from the following detailed description of the present taken conjunction with the drawings. In general, spark used ignition of an internal such a a electrode, insulator provided to the of the center electrode, a shell provided to the a ground electrode installed to the metal shell forming a spark discharge gap between itself the center electrode. The insulator of such spark plug is made of aluminum sintered a rare earth element constituent, a silicon constituent, a group 2 element Japanese Patent No. 4607253, “Patent Document 1”). Conventionally, improvement the strength property been desired for insulator used for spark plug. In improve the strength of composition of the materials of the has optimized or the material has micronized. change in the composition of the material of the insulator is likely to cause the the degradation of a of performance and, further, the micronized material may cause the excessive sinter
 to a data mask instruction sigNal. Each masK gate CirCuiT iNcluDes a Gate circuit for ACtivAting a corresponding datA mask InSTrucTIoN signAl to inhIBiT A CorReSpOndInG WrIte maSk cIrcuit fRom being coNduCtIve when a corrESpOnding writE drIver block is iNacTive.
By VaRyiNG the tImiNg at wHich thE Result Of determiNaTIon is oUTputted IN ThE datA write mode and in thE DaTA read mode, the tiMing foR a COlUMN seLecT can be optiMiZed foR Both a daTA wRITE anD A data read, therEby achievinG A hiGh-speeD aCceSS.
In parTiculAr, BY prOviding a reaD datA bus and a wRite daTA bus sepARately, tHe read DatA anD the WRiTe DatA aRE kePT fRom COllIding witH oNe AnothEr on THE DAta bUs, sO thaT the sO-called xe2x80x9cwRitE recOVerYxe2x80x9D probLem dOeS not oCcur, anD the cYcLe time can be made ShorTer.
Write dRivErS arE dIvideD Into blOckS coRresponDing to tHE reSpECTIvE write mask circuits, AnD A WrIte mask cIrcuit INhIbITs the conNeCtiOn beTWEen a sEnse AMpLifier ciRcuit aND aN iNternal DaTa line. as A reSulT, when A WritE driveR block is In the INactive state, thE Corresponding WRiTE MaSK cirCuiT is activateD and INhibIts a DAtA wrITe opeRatioN sO ThAT the data held by a sensE aMplifiEr cirCuit is kept froM being chanGED, And an accUratE DaTA write operatioN can bE performed EVen when tHe inpUt data biT width is cHANged.
The fOreGoiNg aNd oTHEr Objects, featurES, AspeCtS and advAntAges of tHe pResEnt InvEnTion will bEcome morE aPpArEnT frOm the FOllowing DeTaiLeD deScripTIon of tHe preSent InVeNTioN when taKEn IN ConjUnCtIon wIth ThE accoMpanYIng DrawingS. In generaL, spARk plUgS uSed for iGnition of an inTeRnal combusTiOn eNgine sUCH as a gasoLine engine include a centeR ElectroDe, aN insuLatoR provided To tHe outsIde OF the ceNter elEctroDe, A meTAL shelL PRoVidEd To the outsiDE Of tHe insUlAtor, And a groUnd electrode instalLEd tO the metal shelL anD forMINg A spARk DIscHaRGe gAP Between itself anD the center ElECtRode. The insULatOr Of such sPark pluG is maDE of an alUminum sinTered compAcT conTAIniNg a rare earTh elemenT constituENt, a siLIcOn conStiTuent, aNd A grOup 2 elEment (sEE JaPanesE PatenT NO. 4607253, “PatenT DocuMeNt 1”).
ConvenTionally, improvement in thE dieleCtric StrEngth propErtY Has Been desirEd foR the insulaTor UseD for tHe sPArk plUg. In ORdEr tO ImproVe thE DielectriC StRenGTH pRoperty of thE INSulAtor, tHe cOMpositIon oF the materials of thE Insulator has beEn opTIMizEd oR The mAtErial has been miCroNiZED.
However, ThE change in thE composiTiON of thE materIal of tHe insulATOr IS likelY to cAusE the problEm oF tHE degradAtIoN Of a parT of tHe PerforMance aND, furTHEr, the micronized mAteriAL May caUSe tHe excEsSive sinTEr
 to a data mask instructio n signal.Eachmas k g at e ci rcui t includes a g a te c ircuit for activatinga cor re s pond i ng  data  mask i n st r u cti on  s ign al to  inhi bit  a corr espondingwri te  mask circui t  f rom beingcon ductive when  acorres po ndi n g wri tedrive r bloc k  is in active.
B yv arying the tim i n gat w hich the result o f  d e termination is  outpu tt e di n  th e d ata writemo de an d  in the da t a rea d  mode, the ti ming for ac olu mn sel ec t c a n be o ptimi ze d  fo r both a da ta w rite anda data read, t h ereby a chievi nga h igh- s pe ed  ac ce s s.I npar t icu lar, bypr ov iding  a r e a d data  bu s an d a w rite data bus  se para t ely , the  read  dat aand t he wri te da ta  are kept fromcoll iding wit h o ne  an ot her o n  the d ata  bu s, so t hat the so- ca l l e dxe2x80x9cwrite rec ov e r yx e2x80x9d  probl e mdo e s not oc cu r,andt h e cyc le t i me  can bemade s h or te r.
Writ edriver sare  di vided into  block s corres pondi n g to the respe c tive write ma s kc i rc u its,  an d a write m askc ircu it i n hi bit s  theconne ct i on between a sense amp li fier c ircui t and an inte rnal datal i n e. As aresu l t, when a write d river  block isi n the in activ e state,  the corr e s pondingwri temas k c i r cu it is activat e d  and  i nhibits  adata wr ite  op era tio nso that t he datahe ld  b ya s ensea mplifier  c irc ui t i s kep t  frombeing  cha ng ed ,  an d an ac c ur a t e da ta  w rite  op er ation  can beperform ed even w hen thein pu t databit width isch anged.
The  f ore goinga n d otherobjects, features, aspe c ts andadv antag es o f the pre sen t inve nti o n will  becom e mor eapp a r ent f r o mthe  f ollowing d e t ail ed de sc ript ion ofthe present invent i onwhen taken in  co njun c t io n w i th the  a c com p a nying drawings.  In genera l, sp ark plugsu sed  f or igni tion of  an i n ternalcombustio n enginesu ch a s a g asoline en gine inc lude a ce n ter e l ec trode , a n insu la tor  prov ided t o  th e out side o fthe ce nterel ectrode,  a metal shell provided  to th e out sid e of theins u lat or, and a  gro und electr ode  in stall edt o the  met a lshe l l and  for m ing a spa r kdis c h ar ge gap betw e e n  it selfand the ce nter  electrode. The i n sulator of suc h sp a r k p lug is m ad e of an alumin umsi n t ered com pa ct containi ng a rar ee arthelemen t cons tituent , as ilicon  con sti tuent, an d a  g r oup 2 e le me n t (see  Jap an ese Pa tent N o . 46 0 7 253, “Patent Doc ument 1 ”).
C o nve ntion al ly, imp r ovem ent in the  dielectric  stren gthprope rty has  b een de sir ed  for the i n sulator u sed f or thesp arkplu g. Inorde r to im prov ethe  dielectr i c  s t re ng t h p rope rty o ftheinsulator ,  the com pos i tion of  t hem a terial s  o f the insula tor  hasb e en optimiz e d or th e  mate rial h as bee n micro n ize d. 
Howeve r,t h e changein the co m pos it ionof the m at eria lofth e insulator islikely t o causet h e prob lem of t h e degr ad ation of a p art o ft he perf o r man ce and, fur the r,themic roni z ed material may cause th e ex cessi v e s inter 
 to_a data_mask instruction signal. Each_mask gate_circuit_includes a_gate_circuit for activating_a corresponding data_mask instruction signal to_inhibit a corresponding_write_mask circuit from being conductive when a corresponding write driver block is inactive.
By varying_the_timing at_which_the_result of determination is outputted_in the data write mode_and in_the data read mode, the timing for a_column_select can be_optimized for both a data write and a data_read, thereby achieving a high-speed access.
In_particular, by providing_a_read_data bus and a_write data bus separately, the read_data and the write data are_kept from colliding with one another on_the data bus, so that the_so-called xe2x80x9cwrite recoveryxe2x80x9d problem does_not occur,_and the cycle time can_be made shorter.
Write_drivers are_divided into blocks_corresponding to the respective write mask_circuits, and a_write mask circuit inhibits the connection_between_a sense amplifier_circuit_and_an internal_data line. As_a_result, when_a_write driver block is in the_inactive_state, the corresponding write mask circuit is_activated and inhibits a_data_write operation so that_the data held by a_sense amplifier circuit is kept from_being changed,_and an_accurate data write operation can be performed even when the input_data bit width is changed.
The foregoing_and other objects, features,_aspects and_advantages_of the present_invention_will become_more apparent from the following detailed description_of the_present invention when taken in conjunction_with the accompanying drawings._In_general, spark plugs used for ignition_of an internal combustion engine such_as a gasoline engine include_a_center_electrode, an insulator provided to_the outside of the center electrode,_a metal shell_provided to the outside of the insulator,_and_a ground electrode installed to the_metal_shell and forming a spark discharge_gap_between_itself and the center electrode._The insulator of such spark plug_is made of an aluminum sintered compact containing a_rare earth element_constituent, a silicon constituent, and_a_group_2 element (see Japanese Patent No. 4607253, “Patent Document 1”).
Conventionally,_improvement in_the dielectric strength_property has been desired for the insulator used for the_spark plug. In order to improve the_dielectric strength property of the insulator, the composition of the materials_of the insulator has been optimized or the_material has been micronized.
However, the change in_the composition of the_material_of the insulator is likely to cause_the_problem_of_the degradation of_a part of_the performance and,_further, the_micronized material may_cause the_excessive sinter