Dynamic Shift Registers - Bitsavers - Trailing-Edge

ROM Code ConvertersMM4220BL/MM5220BL baudot-to-ASCII code convertergeneral descriptionThe MM4220BL/MM5220BL is used for conversionof the Communications Set Baudot code to theAmerican Standard Code for Information Interchange(ASCII).The Baudot and ASCII codes have different formats.ASCII has a unique code combination foreach alphabetic, numerical, or control character.The correct interpretation of a five bit Baudot isdependent upon knowing its previous history;whether upper or lower case was last selected, Ineffect a sixth-bit, which can be called the Case Bit,is required to uniquely identify the Baudot input.The latch circuit shown in the typical applicationcan store this information and will generate theCase Bit. If the bit is externally supplied, thefeedback and latch circuits can be deleted (asshown with the X's),The accompanying table is applicable for the codeconversion scheme as shown (or its alternate)rather than for the device itself. The input andoutput codes are defined at the TTL gates with thelogic trues high (Logic "1" = +5 volts, nominal;Logic "0" = Ground, nominal).device characteristicsFor full electrical, environmental, and mechanicaldetails, refer to the MM4220/MM5220 1024-bitread only memory data sheet.typical applicationBaudot to ASCII,INPUT GATE sAREDM881BAUDDTINPUTSBITSBIT4BIT3BIl2BIT I+12Vdc~ALl3.DKIOPTIONAL SIXTH BITFj!I.!!.~~I:!"!!'!.E~E----===:IGATES:OM8IIOOSERIESL.[:'t.12VtIc,. A, 3 12 l1B'V.--'-