Dynamic Shift Registers - Bitsavers - Trailing-Edge

ROM Code ConvertersMM4220BN/MM5220BN arctangent look-up tablegeneral descriptionThe MM4220BN/MM5220BN is a 1024-bit monolithicMaS read only memory that has been programmedto solve for the angle () whose tangentvalue x is known; i.e., to obtain the solution to theequation: () = arctan x.Values of x are defined in the Look Up table foro < x < 1 with angles corresponding from0°;; () < 45°. For values x :::: 1, the reciprocal of x(i.e., 1/x) must be entered and the output anglemust be complemented to obtain the actual value.The input is divided into 128 equal parts for x.Thus, the appropriate input address is (128)(x) tothe nearest whole integer for obtaining the appropriateROM address. The input code is the ROMaddress expressed in binary with Al being the leastsignificant bit. For input values greater than unity,the decimal reciprocal is to be taken prior to entryof the binary address.The output has been normalized for 45°. To obtainthe true angular reading, the output should bemultiplied by 45°, i.e.: () = (()output) x 45° where()output is the decimal equivalent of the output.The output code is the normalized value of theangle () expressed in binary. The output lines B 1 ,B 2 , •••• B8 are binary place values 1/2, 1/4, ....1/256. To obtain angles between 45° and 89.6°which occur when input values of x are equal to orgreater than unity, either complement the outputbinary code and add a 1, or complement theresultant angular value (i.e., subtract from 90°).The 8-bit output code has been rounded off. Thatis, if another bit of even lower significance hadbeen computed for the given arctangent value wasa bi nary" 1", it wou Id have carried over into theLSB of the eight bit code. If it was a binary "0", itwould have been dropped.EXAMPLEFind the angle whose tangent is 0.258.The input address is 128 x 0.258, or 33 to thenearest integer. Expressed in binary, this is0100001, and is the actual input code to theconverter. The converter will generate the binaryvalue .01010010, whose decimal equivalent is0.3203125.Thus, () = 0.320 x 45° = 14.4°device characteristicsFor full electrical, environmental and mechanicaldetails refer to the MM4220/MM5220 1024-bitread only memory data sheet.typical application-12v-----__________.....__4........,"v--...------------+-~+-__4......--""""""l.OK,TYPICAL,7 LINESA, VGG17A,A,A,21A,20A,"B,B,B,B,MM4220BN/ 7M~522DBNB,, B,lOj..:B:!,., ___ -1--1t12V ____ ~...._ .... --V~ss 12 l1~B;:",' ___ +-1UK,TYPICAL,B LINESGATES DM7400b,b,b,b...~,b,b.JtA,"CHIP ENABLE ___...JDTLITTllDGICtMODE CDNTROl----....Jlogic levelsDTL/TTL (ucept at MOS/ROM interface)logk: "1", +!iV, nom. logic "0", ground, nom.MOS/ROM Inputs & OutputLogic"l",mo,e negative. logic "O",more pnsitivetMudeControl = Logic "0"As= Logic "1""Chip Enable = logic "'" to obtain outputs189